QD 

41 
53 


EXCHANGE 


BULLETIN 

or 

THE  UNIVERSITY  OFTEXAS 

NO.  210 

FOUR    TIMES   A    MONTH 

OFFICIAL  SERIES  No. 

Chemistry  in  High  Schools 


BY 


E,  P.  SCHOCH,  PH.  D., 

Professor  of  Physical  Chemistry 
The  University  of  Texas 


PUBLISHED  BY 

THE  UNIVERSITY  OF  TEXAS 

AUSTIN,  TEXAS 

Entered  as  iccond-class  mail  matter  at  the  postoffice  at  Austin,  Texas 


BULLETIN 


OF 

THE  UNIVERSITY  OF  TEXAS 

NO.  210 

FOUR    TIMES    A    MONTH 
OFFICIAL  SERIES  No.   64  DECEMBER  8, 

Chemistry  in  High  Schools 

BY 


E.  P.  ^CHOCH,  PH.  D., 

Professor  of  Physical  Chemistry 

The  University  of  Texas 


PUBLISHED  BY 

THE  UNIVERSITY  OP  TEXAS 

AUSTIN,  TEXAS 

Entered  as  second-class  mail  matter  at  the  postoffice  at  Austin,  Texas 


EXCHANGE 


Acknowledgment. 

Many  teachers  of  science  in  Texas  schools  have  kindly  fa- 
vored the  writer  with  expressions  of  their  experience  on  several 
topics  considered  in  this  paper,  and  their  collective  advice  has 
been  carefully  incorporated.  Indebtedness  is  hereby  grate- 
fully acknowledged. 


WHAT  SOME  OF  OUR  SMALLER  TOWNS  HAVE  DONE  FOR 
CHEMISTRY. 


Chemical    Laboratory,    Winnsboro    (Texas)    High   School. 


Chemical  Laboratory,  Corpus  Christi  (Texas)    High  School. 


WHAT  SOME  OF  OUR  SMALLER  TOWNS  HAVE  DONE  FOR 
CHEMISTRY. 


Chemical   Laboratory,   San  Marcos    (Texas)    High   School. 


Chemical  Laboratory   (on  left),  Eagle  Lake   (Texas)   High  School. 


TABLE  OF  CONTENTS. 

PART  I.      EQUIPMENT. 

Page. 

The  Teacher — Qualifications  . , 9 

When  and  Where  to  Order  Laboratory  Supplies 9 

Selection  of  a  Room  for  the  Laboratory.  .' 10 

Draft  Hoods 11 

Arrangement  of  Desks,  Shelves,  etc.,  in  the  Laboratory.  ...  13 

Details  of  Desks 14 

Plumbing  17 

Cost  of  Desks  and  Plumbing 18 

Other  Furniture 18 

Other  Desk  Designs  and  Ready-Made  Desks 18 

Laboratory  Burners  and  Fuel  Supply 19 

A  Home-Made  Gasoline  Gas  Machine 21 

Source  of  Current  for  Electrolytic  Work 23 

A  Modern  Current  Rectifier 24 

A  Small  Cheap  Current  Rectifier 25 

Supplies  25 

Individual  Outfit 26 

Notes  on  Student's  Outfit 27 

General  Laboratory  Supplies  for  a  Class  of  Twelve  Students  28 

Special  Apparatus  for  Quantitative  Experiments 32 

Apparatus  for  the  Section  of  Electrolysis,  lonisation,  Bat- 
tery Cells,  etc 32 

Apparatus  for  the  Demonstration  of  Combining  Volumes  of 

Gases 33 

Chemicals    33 

Cost  of  Supplies 36 

First  Cost  of  Laboratory 37 

Cost  of  Maintenance  37 

PART   II.       PLAN   AND  CONDUCT   OF   THE   COURSE. 

Main  Object  of  the  Course. 38 

Which  First — Chemistry  or  Physics 38 

Time  Allowance  for  the  Course 38 

Time  Allowance  for  Preparation  of  Laboratory  and  Lecture 

Table  Experiments 39 

Manner  of  Conducting  Laboratory  Work 40 

Note  on  Quantitative  Experiments 41 

The  Note  Book 42 

How  to  Begin  the  Course 44 


TABLE  OF  CONTENTS.  vii 

The  Introduction  of  Symbols  and  of  the  Notions  of  Atoms 

and  Molecules 44 

The  Introduction  of  Valence 46 

The  Fundamental  Facts  of  Electrolysis  and  Its  Introduction 

in  the  Course 46 

General  Discussion  of  an  Outline  for  the  First  Part  of  an 

Introductory  Course 47 

Other  Subjects  That  May  Be  Studied 51 

Experiments  Which  Should  Accompany,  the  Study  of  Avo- 

gadro  's  Hypothesis 53 

Chemical  Information  of  Direct  Economic  Value  in  Texas . .  56 
The  University  of  Texas  Requirements  for  One  Unit 

Entrance  Credit 60 

Some  Suitable  Text-Books  in  Chemistry 60 


PART  III.      OUTLINE  OF  AN  INTRODUCTION  TO  THE  FIRST  PRINCIPLES. 

Oxygen 62 

Hydrogen 63 

Chlorine  64 

Hydrogen  Chloride 65 

Acids.  Bases  and  Salts 65 

Hydration   of  Oxides 67 

Solubility  of  Salts 68 

Table  of  Solubilities  of  Salts 68 

Acid  Salts 69 

Carbon   71 

Sulphur    72. 

Ammonia   73 

Other  Optional  Topics 73 

lonisation,    and   the    General   Relation    Between   Dissolved 

Substances  which  Results  in  Metathetical  Reactions 73 

Exercise  81 

Electrolysis    81 

The  Electro-Motive  Force  of  Galvanic  Cells 87 

Action  of  General  Reagents  Upon  Solutions  of  Salts 91 

Sodium  (or  Potassium)  Hydroxide  as  a  Reagent 91 

Ammonia  as  a  Reagent 93 

Soluble  Sulphides  as  Reagents 95 

Reactivities   of   Sulphides 96 

Colors  of  Sulphides 97 

List  of  Useful  Special  Properties  and  Reactions  of  Metals . .  98 

Chemical  Problems 99 

Text-Book  Reading   100 

Chemical  Changes  Involving  Oxidation  and  Reduction. .  101 


viii  TABLE  OF  CONTENTS. 

Exercise  . 102 

Exercise  104 

Nitric  Acid  and  Its  Reduction  Products 105 

Note  on  the  Oxidizing  Action  of  Sulphuric  Acid 108 

Table  of  Electromotive  Forces  of  Battery  Poles 109 

APPENDIX:   THE   DETAILS  OF   CONSTRUCTION  AND   ACTION  OF   ALTER- 
NATING CURRENT  RECTIFIERS. 

The  Action  of  the  Electrolytic  Cell 113 

Construction  of  Large  Electrolytic  Jars  for  Rectifier  Set 

No.  1 114 

Design  and  Action  of  Special  Transformer 115 

Preparation  of  Solution  for  Electrolytic  Jars 117 

Manipulation  of  the  Rectifier  Set  No.  1 117 

A  Small  Cheap  Rectifier 118 

How  to  Rectify  Both  Alternations  Without  a  Transformer.  .  119 


CHEMISTRY  IN  HIGH  SCHOOLS. 


PART  I :— EQUIPMENT. 

The  Teacher 

First  and  most  important  is  the  teacher.  He  should  be  above 
all  a  science  man,  both  by  inclination  and  training, — a  person 
whose  inclinations  and  desires  naturally  make  him  fond  of  the 
subject.  He  should  have  had  some  sound  training  in  chemistry 
and  he  should  have  received  this  training  at  a  place  where  that 
subject  is  taught  extensively  rather  than  at  a  place  where  only 
introductory  work  is  given,  since  much  necessary  information  is 
absorbed  from  the  proper  "atmosphere."  The  extent  of  the 
person 's  training  in  chemistry  should  not  be  less  than  two  thor- 
ough courses  in  a  first-class  college  or  university,  and  in  addi- 
tion some  college  training  (at  least  one  course)  in  either  physics 
or  in  a  biological  subject  (botany  or  zoology).  This  minimum 
requirement  is  not  excessive,  and  frequently  persons  may  be 
obtained  who  have  had  much  more  training  than  this. 

When  and  Where  to  Order  Laboratory  Supplies. 

The  teacher  who  is  to  use  the  laboratory  should  design  its 
equipment  and  order  the  materials. 

The  supplies  should  be  ordered  early  in  June.  It  is  quite 
profitable  to  submit  large  orders  to  several  of  the  large  import- 
ing houses  for  quotations  for  duty  free  importation  and  deliv- 
ered at  your  railway  station.  If  the  ordering  is  delayed  beyond 
July  1st  it  will  scarcely  be  possible  to  secure  a  duty  free  im- 
portation by  the  time  the  session  opens  in  the  fall.  All  of  the 
large  chemical  dealers  mentioned  in  the  list  below  will  import 
apparatus  duty  free  if  requested  to  do  so. 
C.  H.  Stoelting  Co.,  successors  to  Chicago  Laboratory 

Supply  &  Scale  Co.,  31-45  W.  Randolph  St Chicago,  111. 


1C   '         B •/«*«*„«  University  of  Texas  Bulletin 

Central  Scientific  Co.,  20-28  Michigan  St Chicago,  111. 

Edward  P.  Martin  Co.,  144-146  E.  Erie  St Chicago,  111. 

L.  E.  Knott  Apparatus  Co Boston,  Mass. 

Bausch  &  Lomb  Optical  Co Rochester,  N    Y. 

Woldenberg  &  Schaar,  1025  S.  State  St Chicago,  Til. 

Eimer  &  Amend,  205-211  3rd  Ave New  York. 

The  Kny-Scheerer  Co.,  404  West  27th  St New  York. 

E.  H.  Sargent  &  Co Chicago,  111. 

Selection  of  a  Room  for  the  Laboratory. 

In  the  selection  of  a  room  for  the  chemical  laboratory  the  fol- 
lowing requirements  must  be  met: 

The  room  must  have  such  means  of  ventilation  that  all  fumes 
may  be  removed  rapidly  and  not  blown  into  other  parts  of  the 
building. 

Communicating  with  the  laboratory  there  must  be  a  small 
room  where  the  supplies  may  be  kept  under  lock,  and  in  which 
the  teacher  may  prepare  experiments  and  solutions. 

The  store  and  preparation  room  in  turn  must  communicate 
with  the  class  room  so  that  the  setting  up  and  removal  of  lec- 
ture apparatus  may  be  facilitated. 

If  the  teacher  also  teaches  physics,  then  the  store  and  prepa- 
ration room,  as  well  as  the  class  room,  may  be  used  for  both 
subjects;  but  in  that  case  the  physical  laboratory  should  be 
located  conveniently  near  so  that  apparatus  may  be  transferred 
to  and  from  the  store  room  without  unnecessary  trouble. 

The  simplest  way  to  meet  the  requirement  of  an  adequate 
draft  is  to  select  a  room  with  outer  walls  and  windows  on  at 
least  two  sides.  If  an  inner  room  with  only  one  exposure 
(south!)  must  be  used,  then  there  must  be  provided  at  the  far- 
ther end  of  the  room  from  the  windows  one  or  more  ventilating 
shafts  so  located  that  all  parts  of  the  room  may  be  swept  by  the 
air  current  coming  in  at  the  windows  and  passing  out  through 
the  shafts.  Such  a  shaft  should  be  one  to  two  feet  in  diam- 
eter, and  it  should  extend  straight  to  the  top  of  the  building. 
The  cover  or  cap  on  the  roof  over  the  top  of  this  shaft  should  be 
placed  very  high  (say  twelve  inches)  above  the  top  of  the  shaft, 
so  that  it  will  not  impede  the  draft.  Cornice  men  frequently 


Chemistry  in  High  Schools  11 

place  this  cap  entirely  too  low.     It  is  desirable  to  aid  the  draft 
by  putting  a  gas  flame  or  an  electric  fan  at  the  bottom  inlet. 

The  form  of  ventilators  frequently  employed  for  ventilating 
ordinary  buildings  (that  is,  narrow  shafts  extending  up  in  the 
wall,  and  opening  into  the  rooms  by  means  of  a  series  of  holes 
near  the  ceiling  of  the  room)  provides  insufficient  ventilation  for 
a  chemical  laboratory. 

Draft  Hoods. 

Obnoxious  gases  should  not  be  allowed  to  escape  freely  into  the 
atmosphere  of  the  laboratory,  but  should  be  confined  to  special 
draft  hoods.  Such  draft  hoods  must  be  carefully  designed,  other- 
wise they  are  worse  than  useless.  The  following  rules  should  be 
observed  in  their  design : 

1.  The  hood  should  be  as  small  as  practicable.     More  and 
smaller  hoods  should  be  the  rule. 

2.  The  stack  should  be  vertical  throughout  its  entire  length. 

3.  The  hood  proper,  which  is  the  part  below  the  stack  in 
which  the  apparatus  is  placed,  should  be  as  small  as  possible,  so 
that  the  velocity  with  which  the  air  moves  through  it  may  not 
be  less  than  one-third  of  that  with  which  it  moves  in  the  stack. 
The  velocity  of  the  draft  should  be  great  enough  to  lift  the 
heaviest  vapors,  as,  for  instance,  those  of  sulphuric  acid.     The 
inlet  for  the  draft  should  be  placed  so  that  the  current  of  air 
from  that  point  to  the  chimney  may  sweep  through  all  parts 
of  the  hood.    For  this  purpose  some  stops  are  usually  placed  so 
as  to  prevent  closing  entirely  the  front  door  of  the  hood.     This 
carefully  adjusted  .air  inlet  is  essential  to  the  successful  opera- 
tion of  the  hood.     The  hood  proper  should  be  made  as  low  as 
convenience  will  permit  in  order  that  the  length  of  the  slowly 
moving  air  column  in  the  hood  may  be  as  short  as  possible. 

4.  The  stack  or  chimney  should  be  proportionate  to  the  size 
of  the  hood  and  its  cross  sections  should  not  be  essentially  less 
than  one-third  of  the  cross  section  of  the  hood  proper. 

5.  A  large  gas  burner  should  be  placed  at  the  base  of  the 
stack  at  a  point  at  which  it  is  possible  to  light  the  gas  by  reach- 
ing up  into  the  hood  with  a  burning  candle  on  a  stick.     This 
gas  flame  need  not  always  be  lit  when  the  hood  is  used,  but  in 


12 


University  of  Texas  Bulletin 


la. 


Fiq  1  b, 


Examples  of  Faulty  Hood  Design. 


.2  a. 


front 


Examples  of  Proper  Hood  Design. 
From   the   Chemical   Engineer. 


Chemistry  in  High  Schools  13 

quiet  weather  it  must  be  lit  in  order  to  establish  a  sharp  draft 
in  the  chimney. 

6.  A  cap  covering  the  stack  for  the  purpose  of  keeping  out 
rain  is  frequently  not  necessary  and  naturally  the  hood  will 
operate  best  without  the  cap.  Should  a  cap  be  found  necessary, 
then  care  must  be  taken  to  place  it  very  high  above  the  top  edge 
of  the  stack  in  order  that  the  draft  may  not  be  impeded  by  it. 

Hoods  are  frequently  constructed  without  any  consideration 
of  the  fundamental  principles  to  be  observed  in  order  to  get  a 
good  draft.  Fig.  1-a  shows  a  hood  in  which  the  stack  is  en- 
tirely too  small.  In  Fig.  1-b,  the  stack  suffers  from  the  fur- 
ther impediment  of  not  being  straight.  These  mistakes  in  de- 
sign are  frequently  found  in  actual  hood  construction.  Fig. 
2-a  shows  the  ideal  hood  construction.  In  this  hood  the  stack 
runs  straight  up  from  the  closet  and  is  large  enough  to  provide 
for  a  sharp  draft.  Fig.  2-b  shows  a  mode  of  construction  in 
which  the  closet  is  built  to  connect  with  a  large  flue  in  the  wall. 
If  the  diameter  of  this  flue  is  large  enough  and  a  flame  is  placed 
as  shown,  then  the  hood  will  operate  properly.  All  these  fig- 
ures show  the  form  in  which  the  hood  proper,  or  closet,  is  gen- 
erally built.  The  bottom  of  the  closet  is  usually  at  the  height 
of  the  ordinary  laboratory  desk  and  the  height  of  the  closet 
above  the  table  to  the  contracting  portion  is  30  to  36  inches. 
The  sliding  front  door,  as  well  as  the  two  sides,  should  be  mnde 
of  glass. 

Arrangement  of  Desks,  Shelves,  etc.,  in  the  Laboratory. 

In  the  placing  of  the  laboratory  desks  and  the  supply  shelves 
care  must  be  taken  to  leave  enough  room  for  the  students  and 
instructor  to  pass  each  other  and  secure  their  supplies  readily. 
The  distance  between  the  desks  should  be  4  ft.  6  in.,  certainly 
not  less  than  4  ft.  Desks  should  not  be  placed  adjacent  to  the 
wall  anywhere,  and  a  space  at  least  6  ft.  wide  should  be  left 
between  the  wall  and  the  desks  all  around  the  room.  However, 
this  space  is  large  enough  to  place  shelves  along  the  wall 
wherever  desired,  as  well  as  shelves  for  blast  lamps,  balances,  and 
other  special  apparatus.  It  is  advisable  to  place  a  platform  with 
a  suitable  table  and  a  black-board  in  the  room  so  situated  that 


14  University  of  Texas  Bulletin 

the  instructor  may  make  special  demonstrations  before  the  class 
or  give  special  explanations  while  laboratory  work  is  in  progress. 

In  placing  the  desks,  the  manner  of  running  the  gas,  water 
and  sewer  mains  should  be  considered:  It  is  most  desirable  to 
run  these  underneath  the  ceiling  of  the  room  below  the  labora- 
tory— hence  open  to  view  and  accessible  for  repairs  at  any  time ; 
this  permits  the  placing  of  the  desks  in  any  way  desired.  If, 
however,  the  pipe  mains  must  be  placed  in  the  floor,  then  they 
should  run  so  as  not  to  cross  the  floor  joists,  and  the  desks  must 
be  placed  accordingly.  The  floors  over  the  pipe  mains  should 
not  be  nailed  down  again,  but  made  "trap-door"  fashion. 

There  should  be  no  high  shelves  or  other  super-structure  on 
top  of  the  laboratory  desks  which  would  prevent  the  instructor 
from  looking  across  the  room  and  seeing  what  is  on  top  of  any 
desk.  The  sets  of  reagent  bottles  are  to  be  placed  on  small,  low, 
movable  shelves,  36  to  40  inches  in  length,  designed  to  hold  one 
row  of  bottles  on  each  side,  with  a  partition  at  the  centre  not 
over  six  inches  high.  The  bottoms  of  the  shelves  should  be  six 
inches  "clear"  above  the  table  top,  but  the  total  height  of  the 
shelf  and  bottles  should  not  exceed  12  to  14  inches. 

Details  of  Desks. 

In  most  schools  the  laboratory  is  to  be  used  by  two  sets  of 
students  on  different  days.  This  is  easily  arranged,  because  the 
amount  of  desk  top  space  required  by  a  student  while  working 
is  large  enough  to  construct  two  independent  lockers  under- 
neath it.  In  some  cases  instructors  have  even  arranged  for  three 
independent  lockers  under  this  space  so  that  the  laboratory  may 
be  used  by  three  distinct  groups  of  students  at  different  periods. 
They  place  four  deep  drawers  in  the  space  of  the  two  lockers 
used  in  the  former  arrangement : — three  of  these  are  locked  sep- 
arately and  in  them  are  placed  the  perishable  apparatus  dealt 
out  to  the  students  individually.  The  fourth  is  not  locked  and 
in  it  are  placed  the  iron  ring  stand,  the  wooden  funnel  stand, 
the  burners  and  other  large  and  usually  non-breakable  appa- 
ratus to  be  used  by  three  students  in  common.  This  arrange- 
ment is  not  as  convenient  as  the  two  student  arrangement. 

The  table  top  space    allowed    per    student,    while    at   work, 


Chemistry  in  Hi<jh  Schools  15 

should  be  42  inches  in  width,  and  24  inches  in  depth  The 
desks  should  be  36  inches  high.  Each  student  should  have  for 
his  use  two  gas  cocks  and  between  each  of  the  two  students 
working  together  there  should  be  a  water  faucet  and  a  sink. 
These  should  be  placed  in  the  center  of  the  desks  so  as  to  be 
accessible  from  both  sides,  and  hence  be  used  by  four  students 
in  common.  The  pipes  run  from  one  end  of  the  desk  under- 
neath the  top  along  the  center  of  the  desk. 

Each  locker  should  be  closed  by  a  large  door  hinged  so  that 
when  open  it  may  be  folded  back  upon  the  unused  locker.  The 
lower  part  of  the  cupboard  should  be  left  open  to  a  height  of 
26  inches,  and  in  it  should  be  placed  a  shelf  12  inches  wide 
placed  8  inches  above  the  floor  in  the  back  of  the  cupboard.  In 
the  upper  part  of  the  cupboard  there  should  be  a  drawer  the 
size  of  which,  however,  need  not  occupy  the  whole  free  space, 
which  is  eight  inches;  instead,  the  drawer  need  be  only  3l/z 
inches. high.  The  partition  between  the  two  sets  of  cupboards 
facing  each  other  may  be  made  of  the  cheapest  sort  of  lumber- 
boxing.  It  should  be  placed  2  to  3  inches  "off-centre,"  so  that 
the  pipes  may  be  placed  along  the  centre.  The  side  partitions, 
that  is,  those  at  the  ends  of  the  desks  and  between  the  indi- 
vidual lockers,  may  be  made  of  ceiling,  the  strips  running 
vertically.  The  door  also  may  be  made  of  ceiling  and  the 
hinges  should  be  placed  so  that  screws  cannot  be  drawn  when 
the  door  is  closed.  Stout  hasps  should  be  supplied  with  which 
to  lock  each  door.  For  further  details  of  construction  see 
Fig.  3.  The  tops  may  be  made  of  flooring;  though  it  is  advis- 
able to  make  them  of  114  inch  white  pine,  or  cypress.  The  surface 
should  be  covered  twice  with  a  half-saturated  solution  of  par- 
affin in  gasoline,  and  it  should  be  covered  once  at  intervals  of 
a  year  or  so.  This  is  a  better  surface  treatment  for  these  desks 
than  most  other  "so-called  acid  proof"  treatments.  The  solu- 
tion is  prepared  by  saturating  some  gasoline  with  finely  sliced 
paraffin,  and  then  adding  an  equal  volume  of  gasoline  to  the 
solution. 

The  desks  should  not  be  too  long:  14  ft.  is  the  maximum 
length  desirable;  such  a  desk  contains  16  lockers,  and  top 


16 


University  of  Texas  Bulletin 


o| 


c=J 


Chemical  Laboratory  Desk. 


Chemistry  in  High  Schools  17 

space  for  eight  students  working  simultaneously  four  on  each 
side.  It  is  advisable  to  make  the  desks  only  half  as  long,  that 
is,  with  only  4  lockers  to  the  side,  and  then  to  place  sinks  at 
the  ends  of  the  desks. 

Plumbing. 

It  is  unnecessary  to  "trap"  each  one  of  the  sinks  separately; 
the  main  pipe  only  needs  to  be  trapped  at  some  convenient 
point;  or  better  still,  it  may  empty  into  a  "hopper/  The  lat- 
ter acts  also  as  a  sieve  to  catch  solids,  etc.,  and  thus  prevents 
the  choking  up  of  the  sewer  beyond  the  hopper. 

The  desks  should  be  so  arranged  that  the  main  pipes  pass  up 
the  center  or  one  side  of  the  laboratory  so  as  to  touch  the  end' 
of  each  desk.  Of  course,  the  size  of  these  mains  depends  on 
the  number  of  desks.  In  the  laboratory  to  which  the  accom- 
panying figures  refer,  built  to  accommodate  236  individual 
Icekers,  the  sewer  main  is  a  cast  iron  pipe  4  inches  in  diameter, 
the  water  main  is  a  2  inch  pipe  and  the  gas  main  is  a  2  inch 
pipe.  The  laterals  for  a  16  locker  desk  unit  as  used  in  this 
laboratory  are  of  the  following  dimensions :  drain  pipe,  2 
inches  (cast  iron)  ;  water  and  gas,  one  inch  each.  Where  the 
drain  pipe  comes  out  of  the  desks  and  turns  downward,  a  "1 '" 
should  be  placed  instead  of  an  elbow.  By  this  means  an  ob- 
struction in  the  pipe  may  be  readily  dislodged.  Here  the  pipes 
should  be  joined  by  a  union  in  order  that  a  desk  may  be  easily 
'lisconnected. 

The  sinks  may  be  of  porcelain :  a  14  inch  hemispherical  bowl 
such  as  may  be  obtained  for  about  one  dollar,  or  a  little  above, 
will  serve  the  purpose  very  well.  It  should  not  be  fastened  to 
the  drain  pipe,  but  the  spout  should  merely  extend  into  a  short 
piece  of  lead  pipfe  connecting  with  the  drain  pipe.  Sinks 
placed  at  the  ends  of  desks  should  be  of  rectangular  form,  lead 
lined,  16  by  20,  and  10  in.  deep  inside.  A  water  faucet  of 
the  ordinary  bar-fixture  type,  will  be  found  suitable.  When  in 
use  a  short  piece  of  rubber  tubing  should  be  attached  to  the 
faucet  to  prevent  any  splashing  of  water. 

The  gas  cocks  should  be  chosen  carefully  so  as  to  fit  the*  size 
of  rubber  tubing  used  on  the  Bunsen  burners.  The  gas  cocks 
commonly  used  by  plumbers  for  dwellings  are  entirely  Uo 
large  for  this  purpose. 


18  University  of  Texas  Bulletin 

Cost  of  Desks  and  Plumbing. 

At  present  the  cost  of  desks  made  according  to  this  design 
is,  in  Austin,  approximately  four  dollars  per  locker.  The 
plumbing,  including  mains,  etc.,  is  about  $1.50  per  locker  ad- 
ditional. 

Oilier  Furniture. 

One  or  several  hoods  will  be  required.  It  is  difficult  to  give 
an  estimate  of  these  because  the  cost  depends  entirely  upon  the 
design.  However,  the  hood  proper  without  the  stack  need  not 
cost  more  than  $15  to  $18. 

The  store-room  and  the  teacher's  work  room  should  be  sup- 
plied with  large,  commodious,  plain  shelves,  for  the  stock  of 
supplies,  etc.  Placed  in  a  separate,  well-closed  small  room,  as 
they  should  be,  they  need  no  doors  to  keep  out  the  dust,  and 
su(-h  open  cupboards  are  much  more  practical  than  closed  cup- 
boards. The  teacher's  room  should  also  have  a  commodious 
table  supplied  with  gas,  and  a  large  sink. 

Other  Desk   Designs   and  Ready-Made  Desk*. 

Tn  many  schools  individual  desks  are  now  used,  ani  they  are 
arranged  so  that  all  the  students  face  in  the  same  direction. 
Furthermore,  a  space  is  left  beneath  them  so  that  a  student  can 
sit  conveniently  upon  a  stool  while  doing  his  work.  Such  a 
desk  can  be  readily  designed  by  taking  the  space  occupied  by 
two  cupboards  in  the  former  design,  adding  to  it  about  20  inches 
for  the  open  space  beneath  where  the  student  puts  his  feet  in 
•sitting,  thus  making  a  unit  of  62  inches  width,  about  30  inches 
depth  and  36  inches  height.  The  two  cupboards  are  placed  on 
the  two  sides  with  the  central  open  space  between  them.  The 
-water,  gas  and  sink  may  be  placed  anywhere  on  the  back  part 
•of  the  desk,  though  they  are  usually  placed  in  the  space  between 
the  two  lockers  and  as  near  the  back  edge  of  the  top  as  is  pos- 
sible. The  cost  of  this  construction  is  necessarily  greater  than 
that  mentioned  above.  Inclusive  of  plumbing,  it  cannot  be  less 
than  $20.00  per  desk  with  two  lockers,  even  if  it  is  constructed 
as  cheaply  as  possible. 


Chemistry  in  High  Schools  19 

Frequently  school  authorities  not  wishing  the  trouble  of  con- 
structing desks,  desire  to  secure  them  ready  made  from  some 
reliable  business  firm.  Desks  built  by  manufacturers,  who 
make  a  specialty  of  such  work,  present  many  points  of  advan- 
tage ;  they  are  generally  well  designed  and  well  made.  Naturally 
their  cost  will  be  much  greater  than  the  cost  of  the  simple  desks 
mentioned  above.  The  following  parties  make  a  specialty  of  man- 
ufacturing laboratory  furniture,  and  it  is  advisable  to  obtain  the 
catalogues  of  several  houses  while  studying  this  matter: 

The  Kewaunee  Manufacturing  Co.,  (Catalogue  No.  4),  Ke- 
waunee,  Wis. 

Leonard,  Peterson  &  Co.,  1240  Fullerton  Ave.,  Chicago,  111. 

L.  E.  Knott  Apparatus  Co.,  Boston,  Mass. 

The  best  design  of  an  individual  desk  found  on  the  market  is 
that  of  the  Altaffer  Individual  Desk,  which  is  designed  and 
manufactured  by  L.  B.  Altaffer,  1445  Wyandot  Ave.,  Cleveland, 
Ohio. 

Laboratory  Burners  and  Fuel  Supply. 

The  alcohol  lamp  is  so  feeble  that  nearly  all  teachers  agree 
in  reporting  it  as  absolutely  unsatisfactory. 

The  small  gasoline  torch  sold  by  all  dealers  (e.  g.  Central 
Scientific  Co.,  Cat.  No.  4449),  is  reported  as  quite  satisfactory 
by  some  teachers  and  as  unsatisfactory  by  others.  The  dif- 
ference in  opinion  is  probably  due  to  the  fact  that  the  valves 
of  the  pump  do  not  last  longer  than  one  session  and  then, give 
much  trouble;  again,  the  gasoline  must  be  filtered  through  a 
chamois  bag,  si-nee  otherwise  the  small  gasoline  vent  in  the 
burner  is  choked  up  frequently.  Usually  repairs  have  to  be 
made  by  the  teacher,  hence  with  heavy  laboratory  work,  and 
more  than  a  few  students,  the  loss  of  time  caused  by  these 
burners  becomes  prohibitive. 

The  valve-less  gasoline  burner  (e.  g.  Central  Scientific  Co., 
Cat.  No.  4455)  is  rather  feeble  and  exceedingly  troublesome, 
hence  it  is  not  to  be  recommended. 

Acetylene  gas  may  be  burned  in  a  Bunsen  burner  of  special 
construction  (Central  Scientific  Co.,  Cat.  No.  4632).  It  is  a 
very  convenient  and  satisfactory  sourse  of  heat,  but  its  cost 
appears  to  be  prohibitive. 


20  University  of  Texas  Bulletin 

Gasoline  Gas  Machines.  There  are  at  least  three  distinct 
machines  of  this  sort  on  the  market:  the  F-P  Gas  Machine, 
sold  in  this  state  by  the  Texas  Lighting  Co.,  Box  687,  Dallas; 
the  Standard  Vacuum  Gas  Machine,  manufactured  by  the 
Standard-Gillett  Light  Co.,  9-11  West  Michigan  St.,  Chicago; 
and  the  Tirrill  Gas  Machine,  manufactured  by  the  Tirrill  Gas 
Machine  Ltg.  Co.,  509  Fifth  Aye.,  New  York.  See  also  the 
Home-Made  Machine  farther  on. 

The  smallest  unit  of  the  F-P  Gas  Machine  is  for  five  burners, 
and  the  prices  up  to  the  fifteen  burner  size  are  much  smaller 
that  the  price  of  the  smallest  unit  (twenty-five  burners)  of  the 
cheaper  one  of  the  other  machines ;  but  for  a  larger  number  of 
burners  the  others  are  at  least  as  cheap,  when  all  is  considered, 
and  they  are  certainly  to  be  preferred.  The  writer  has  not  seen 
the  F-P  machine  in  operation,  but  he  really  doubts  that  it  is 
suitable  for  chemical  laboratories  because  the  burners  are  perma- 
nently attached  to  the  supply  pipes,  and  the  number  of  burners 
can  be  increased  only  by  having  the  makers  put  in  the  additional 
equipment. 

The  two  other  gas  machines,  the  Tirrill  and  the  Standard 
Vacuum,  are  practically  of  the  same  type,  and  of  quite  a  dif- 
ferent type  from  the  F-P  machine.  Of  the  Tirrell  machines 
there  are  several  now  in  successful  operation  within  the  state. 
Both  machines  are  furnished  in  several  sizes,  the  smallest  of 
which  furnishes  gas  for  25  lights.  As  quoted  to  the  writer,  the 
price,  of  the  Standard- Vacuum  Machine  is  considerably  less 
than  the  price  of  the  Tirrill.  Attention  must  be  called  to  the 
fact  that  the  prices  for  these  machines  are  f.  o.  b.  factories,  and 
that  the  cost  of  their  installation  is  considerable. 

Although  the  purchase  of  one  of  these  machines  may  appear 
to  be  an  unduly  large  expenditure  for  this  one  need,  namely, 
that  of  fuel,  yet  it  must  not  be  forgotten  that  these  machines 
furnish  the  best  fuel  for  laboratory  purposes  and  save  on  other 
expenses,  first  of  all  on  the  cost  of  the  burners,  and  second  in 
saving  the  time  which  is  otherwise  lost  by  both  the  teacher  and 
the  pupil  in  keeping  the  other  kinds  of  lamps  in  operation. 
Hence  for  a  class  of  20  or  more  a  machine  of  this  sort  is  much 
more  economical  than  a  number  of  gasoline  blast  lamps  plus  the 
cost  of  time  for  their  operation.  But  even  for  smaller  classes, 


Chemistry  in  High  Schools 


21 


A  Home-Made  Gasoline  Gas  Machine. 

for  instance,  of  10  students,  the  extra  expense  involved  in  the 
purchase  of  such  a  machine  will  be  balanced  by  the  saving  in 
several  years. 

.1  Ilo*n<  -Made,  Inexpensive,  G-asoline-Gas  Machine. 

A  home-made,  inexpensive  gasoline-gas  machine  was  installed 
in  the  Mexia  High  School  last  summer  and  it  has  been  in  suc- 
cessful operation  during  the  fall.  Mr.  A.  G.  Koenig,  who  de- 
signed and  installed  it,  has  kindly  furnished  the  following  de- 
scription of  it: 

The  gasoline  gas  machine  now  in  use  in  the  Mexia  High  School 
consists  of  four  parts:  1.  The  pump.  2.  The  air  tank.  3. 
The  carburater  and  gasoline  tank.  4.  The  source  of  power. 
These  are  assembled  as  shown  in  Fig.  4.  The  pump  used  is  one 
having  an  internal  diameter  of  1.12  inches,  the  stroke  is  about  4 


22 


University  of  Texas  Bulletin 


inches,  and  running  at  the  rate  of  150  strokes  per  minute  it  fur- 
nishes about  1-4  cu.  ft.  of  air  per  minute,  which  is  enough  to 
supply  12-15  Bunsen  burners  with  the  gasoline  gas.  This  pump 
was  obtained  from  the  Columbia  School  Supply  Co.,  Indianap- 
olis, Indiana,  at  $4.90.  The  air  tank  is. a  No.  1827  pressure  tank 
sold  by  Columbia  School  Supply  Co.  for  $3.75. 


Mechanical  Power  for  Gas  Machine. 

The  carburater  consists  of  a  five  gallon  oil  can  which  can  be 
bought  for  $0.60,  and  about  3  ft.  of  1-4  inch  lead  tube  closed 
at  one  end  and  coiled  up  in  the  bottom  of  the  can  as  shown  in  the 
diagram.  A  large  number  of  very  fine  holes  were  made  in  this 
lead  coil  by  means  of  a  sewing  needle  or  a  fine  awl.  The  air 
passing  through  these  numerous  holes  in  the  coil  at  the  bottom 
of  the  gasoline  becomes  saturated  with  gasoline  vapor.  It  is 
advisable  to  place  two  rolls  of  wire  gauze  in  the  iron  pipes  con- 


Chemistry  in  High  Schools  2S 

veying  the  gas  from  this  carbureter  to  the  laboratory;  this  pre- 
vents the  flashing  back  of  the  flame  through  the  pipes.  Instead 
of  the  ordinary  Bunsen  burner  it  is  advisable  to  use  one  in  which 
the  air  and  the  gas  supplies  may  be  independently  and  accu- 
rately regulated.  The  expense  for  gasoline  during  the  past 
three  months  has  been  about  one  cent  per  hour  for  ten  burners. 

The  air  pump  is  driven  by  a  six-inch  water  motor  manufac- 
tured by  the  Divine  Water  Motor  Co.  of  Utica,  N.  Y.,  price  $5.00. 
The  pulleys  and  mechanism  for  applying  the  power  to  the  pump 
were  obtained  by  adapting  the  foot-power  mechanism  of  an  old 
sewing  machine  at  a  cost  of  $2.00. 

There  would  be  no  difficulty  in  substituting  a  small  electric 
motor  (say  a  strong  fan  motor)  for  the  water  motor  above. 

Where  neither  electric  nor  water  power  is  available  the  fol- 
lowing device  may  be  used  as  a  source  of  power:  A  derrick 
consisting  of  four  2x4  scantlings,  well  braced,  and  about  20  ft. 
high  is  used  to  raise  a  strong  box  filled  with  sand  or  other  heavy 
objects.  In  order  to  have  enough  rope  or  wire  cable  to  wind  on 
the  drum,  a  system  of  pulleys,  consisting  of  3  or  4  fixed  at  the 
top  and  2  or  3  at  the  bottom,  is  used.  This  will  give  100  or  140 
ft.  of  rope  to  be  wound  on  the  drum.  The  mechanism  of  the 
whole  device  is  shown  in  Fig.  5. 

The  large  cog-wheel  a  and  the  drum  &  run  on  the  same  axle. 
The  rachet  c  allows  the  drum  to  be  turned  from  right  to  left  in 
winding  up  the  weight. 

Source  of  Current  for  Electrolytic  Work. 

As  a  rule,  electrolytic  work  requires  a  direct  current  of  low 
voltage.  At  present  this  is  obtained  either  from  battery  cells 
(dry  cells),  or  from  high  voltage  (110  volts)  direct-current  light- 
ing systems  by  wasting  nine-tenths  of  the  energy.  Both  of  these 
sources  are  inefficient,  uneconomical,  or  troublesome,  and  it  is 
desirable  to  secure  a  better  source.  This  is  obtained  by  trans- 
forming and  rectifying  the  alternating  lighting  current  which  is 
found  even  in  the  smallest  towns.  Since  no  really  first-class, 
modern  apparatus  for  this  purpose  appears  to  be  in  the  market, 
the  following  detailed  description  for  securing  such  is  here  given. 

Two  distinct  rectifying  sets  are  described  below.     The  first 


24 


University  of  Texas  Bulletin 


is  the  best  design  for  this  purpose  that  can  be  made  at  present. 
It  naturally  costs  more  than  the  second,  but  even  its  cost  is  much 
less  than  the  cost  of  anything  offered  in  the  market  that  could 
take  its  place.  In  both  sets  the  electrolytic  jars  or  rectif yet- 
proper  can  be  easily  assembled  at  home,  as  well  as,  and  perhaps 
better  than,  it  is  done  by  the  manufacturers;  and  at  much  less 


fia.6.  AC 

Mam 


A  Modern  Current  Rectifier. 


cost.  The  second  represents  the  design  followed  by  many  manu- 
facturers; a  combination  of  a  lamp-bank  rheostat  with  the 
rectifier  proper.  The  particular  form  here  described  costs  only 
a  trifle,  and  is  very  easily  constructed. 

(1)  A  current  rectifier  for  10  amperes  direct  current  and 
any  pressure  up  to  45  volts.  This  apparatus  consists  of  the 
following : 


Chemistry  in  High  Schools  25 

(a)  A  specially  designed  transformer  (price,  $13.00,  f.  o.  b., 
St.  Louis,  Mo.,  Moloney  Electric  Co.).    For  details  see  p.  116. 

(b)  Two  electrolytic  jars  (or  one  double-jar)  ;  approximate 
cost  of  material  .$2.50 ;  for  details  of  construction,  see  p.  114. 

(c)  Three  double-pole,  double-throw  switches  (smallest  Bry- 
ant Baby  Knife  switches  on  porcelain  bases)  ;  secure  locally  or 
from  Western  Electric  Co.,  approximate  price,  $1.50. 

(d)  Two  binding  posts,  30  cts. 

(e)  One  rheostat  with  approximately  10  ohms  resistance  and 
a  current  capacity  of  10  amperes  on  at  least  a  part  of  the  rheo- 
stat.   A  Ward-Leonard  Co.  (Bronxville,  N.  Y.)  Field  Rheostat, 
FF  810,  price  $5.80,  or  FF  820,  price  $7.30,  will  be  found  to 
be  very  serviceable,  and  probably  cheaper  than  other  equivalent 
rheostats.    The  whole  is  to  be  assembled  as  shown  in  Fig.  6. 

This  apparatus  operates  extremely  economically  and  admits 
of  convenient  regulation  to  any  desired  current  or  voltage. 
Both  alterations  of  the  alterating  current  are  "rectified,"  mak- 
ing the  direct  current  obtained  practically  continuous.  It  is 
just  as  serviceable,  and  cheaper  than  a  storage  battery.  The 
nearest  approach  to  it  in  the  market  is  a  four- jar  rectifier  (see 
page  119  combined  with  a  lamb-bank  rheostat,  the  cost  of 
which  is  as  much,  if  not  more,  than  this,  while  it  is  not  nearly  as 
serviceable. 

(2)  A  cheap  small  current  rectifier.  This  apparatus  is  de- 
signed for  a  maximum  of  about  3  amperes,  at  4  to  8  volts ;  the 
total  cost  of  material  for  the  apparatus  is  about  $3.50,  and  it  can 
be  made,  i.  e.  assembled,  in  one  or  two  hours.  It  will  be  found 
much  cheaper,  more  convenient,  and  more  serviceable  tlian  pri- 
mary batteries  or  dry  cells.  The  details  for  construction  are 
given  on  page  118.  Only  one  alternation  of  the  alternating 
current  is  rectified,  giving  a  pulsating  current.  However  it  is 
just  as  serviceable  for  electrolytic  work  as  a  continuous  current. 

The  details  for  construction,  action,  and  operation  of  rectify- 
ing sets  are  given  at  length  on  page  113. 

SUPPLIES. 

These  lists  of  apparatus  and  chemicals  include  all  that  is 
needed  for  the  work  given  in  most  .text-books,  and  also  for 
the  work  outlined  in  this  paper,  with  the  possible  omission 


26  University  of  Texas  Bulletin 

of  a  few  things  which  are  easily  obtained  locally.  Naturally, 
special  experiments  Driven  in  particular  laboratory  manuals 
are  not  provided  for  here,  but  since  nearly  all  modern  lab- 
oratory manuals  give  lists  of  the  apparatus  and  chemicals  needed, 
the  extra  material  may  be  easily  added.  This  list  calls  for  some- 
what larger  quantities  than  those  given  in  the  manuals,  but  these 
larger  quantities  will  be  found  very  desirable. 

In  ordering  supplies,  an  individual  set  should  be  secured  for 
the  teacher.  Of  the  perishable  material,  half  as  much  again  as  is 
necessary  for  the  individual  sets  should  be  secured. 


Individual  Outfit. 

1  Burner,    either   a   Bunsen   burner  with  2   ft.  of   rubber 
tubing  of  best  white  rubber  wrapped  in  cloth,  diam.  11x6 .  $  .50 
or  a  gasoline  torch  ($2.75.) 

1  Wing  top  (for  Bunsen  burner  only) 10 

1  Iron  stand  (24  inches)  with  three  rings 65 

1  Iron  burette-clamp  and  clamp-holder 35 

1  Burette  50  cc.  with  glass  stop-cock  (See  Note  1) 70 

1  Deflagrating  spoon 03 

1  Piece  of  wire  gauze,  iron,  heavily  tinned,  5  "x5  " 07 

1  Piece  of  asbestos  board  5"x5"  ys"  thick  (See  Note  2) . .     .02 

2  Porcelain  evaporating  dishes :  1-3 ' ' ;  1-5  " 25 

1  Small  mortar  and  pestle  of  wedgewood,  3%  to  4"  in 

diameter  40 

1  Wash  bottle  (1000  cc.)  with  rubber  stopper  and  glass 

tube  fittings  (See  Note  3) 30 

1  Nest  of  4  beakers— 50  cc.,  150  cc.,  250  cc.,  400  cc 40 

1  Crucible  Tongs  50 

1  Porcelain  Crucible  with  lid,  18cc 20 

1  Clay-covered  Iron  Triangle 03 

2  or  3  Wide  Mouth  (or  salt  mouth)  Bottles,  500  cc.     (See 
Note  7) 20 

.2  or  3  Pieces  of  Window  Glass,  4x4. .  .10 


Chemistry  in  High  Schools  27 

12  Test-tubes,   16-160  mm.   .01  each 12 

1  Test-tube  rack  with  pins 28 

1  Dropping  Funnel  with  cylindrical,  open  top,  50  cc.  capac- 
ity ;  stem  length,  12  cm.,  diam.  6  mm 40 

1  Test-tube   Holder    (wire) 08 

2  Glass  Funnels :  2% ' '  and  3% ' '  respectively 25 

1  Test-tube   Brush 03 

1  Wooden  Funnel  Stand  for  2  funnels 60 

1  Triangular  File  (See  Note  4) 05 

1  Pneumatic  Trough  (See  Note  5) 35 

1/2  Pack  (50)  Filter  papers  12  %  cm.  (5") 10 

1  Thistle  Top'Funnel  tube,  length  12  in.,  diam.  of  stem,  6mm    .03 

1  Graduate,  or  one  open  top,  graduated,  cylinder,  100  cc.  .     .15 

2  Erlenmeyer  Flasks  with  two  hole  rubber  stoppers  to  fit.  .     .40 
1  flask-250  cc.  with  No.  3  or  No.  4  rubber  stopper :  1  flask- 

400  cc.  with  No.  4  or  No.  5  rubber  stopper  (See  note  6). 

2  Watch  Glasses:  3"  and  5" 20 

3  ft.  Glass  Rodding,  diameter  3mm.,  per  Ib 50 

10  ft.  Glass  Tubing,  diameters  6x4  mm.  or  5x3  mm.,  per  Ib.     .12 
2  Hard  Glass  Test-Tubes  of  best  hard  glass,  18x160  mm. . .     .20 
1  Porcelain   spoon  and  spatula,  length   10  cm.,  width  of 

spoon,  14mm 10 

1  Piece  of  platinum  wire,  No.  28  B.  &  S.  gage,  length  5  cm. 

fused  into  the  end  of  a  piece  of  glass  rodding 16 

1  Piece  of  black  rubber  tubing,  length  12  inches,  diameters 

7x4  mm !20 

Notes  on  Student's  Outfit. 

(1)  All  ground  glass  stop-cocks  should  be  taken  out  and  tied 
on  the  apparatus  when  not  in  actual  use. 

(2)  This  piece  of  asbestos  board  is  to  be  used  in  place  of  a 
water  bath,  and  for  elementary  work  is  much  more  serviceable. 
Should  a  water  bath  be  absolutely  required,  then  a  large  size 
beaker  will  probably  serve  the  purpose.     No  water  bath  is  in- 
cluded in  the  list. 

(3)  Buy  flat  bottom,  1  liter,  Bohemian  flasks,  cover  the  necks 
with  cord,  secure  two  hole  rubber  stoppers  to  fit  mouth  of  .flask 
(probably  No.  6  rubber  stopper),  and  during  one  of  the  earliest 


28  University  of  Texas  Bulletin 

laboratory  periods  teach  the  student  how  to  make  the  glass-tube 
fittings. 

(4)  Purchase  the  triangular  files  by  the  dozen  from  a  local 
hardware  dealer. 

(5)  Buy  small  dish  pans  and  paint  these  inside  and  out  with 
asphalt  paint ;  they  will  serve  the  purpose  just  as  well  as  the  more 
expensive  regular  pneumatic  troughs. 

(6)  These  flasks  with  the  rubber  stoppers  serve  as  generating 
flasks,  as  gas  wash  bottles,  etc. 

(7)  Almost  any  sort  of  a  wide-mouth  bottle   (pickle  bottle, 
fruit-jars,  etc.)  may  serve  for  these  bottles.     The  pieces  of  glass 
to  be  used  as  covers  may  be  supplied  by  a  local  dealer. 

(8)  All  rubber  ware,  i.  e.  stoppers  and  tubing,  when  not  in 
actual  use,  should  be  disconnected,  or  tubes  drawn  out  of  stop- 
pers, etc.,  and  should  be  laid  away  in  the  dark,  since  light  de- 
composes rubber  rapidly. 

General  Laboratory  Supplies  for  a  Class  of  Twelve  Students. 

One  blast  lamp  and  foot  bellows  for  gas  (or  a  large  gasoline 
torch.)  There  is  no  foot  blower  listed  by  American  dealers  that 
is  as  satisfactory  and  as  lasting  as  the  one  listed  by  Dr.  Bender 
and  Dr.  Hobein,  Munich,  Germany,  Cat.  No.  2201.  The  blower, 
No.  2  diameter  30  cm.  is  listed  at  40  mark  ($10.00)  and  is  quite 
satisfactory.  No.  2245  in  the  same  catalogue  gives  an  extremely 
useful  blast  lamp  (list  price  $3.00)  to  be  used  with  the  blower. 
A  blast  lamp  outfit  is  not  absolutely  necessary  but  is  extremely 
desirable.  By  its  means  a  teacher  can  make  many  pieces  of  sim- 
ple glass  apparatus,  which  otherwise  is  impossible.  Simple  glass- 
blowing  can  and  should  be  mastered  by  every  teacher  of  chemis- 
try Helpful  hints  on  glass-blowing  are  found  in  the  booklet: 
Shenstone,  "The  Methods  of  Glassblowing. "  (Longmans,  Green 
&  Co.) 

Six  sets  of  eight  desk  reagent  bottles,  with  labels  blown  in  the 
glass,  capacity  500  cc. ;  with  ground  glass  stoppers  (except  where 
marked).  ,  (One  set  for  every  two  students  working  simulta- 
neously and  one  extra  set  for  the  teacher). 


Chemistry  in  High  Schools  29 


Concentrated  Sulphuric  Acid  ..................  , 

Dilute  Sulphuric  Acid  ...................... 

Concentrated   Hydrochloric   Acid  .............. 

<fc-|  Q 

Dilute  Hydrochloric  Acid  ....................... 

-     for 
Concentrated  Nitric  Acid 


Dilute  Nitric  Acid  ...............  .  ........... 

Ammomium   Hydroxide  ....................... 

Sodium  Hydroxide   (rubber  stopper)  ........... 

50  to  75  solution  bottles  for  the  general  side  shelf  in  the  lab- 
oratory ;  capacity,  500  cc.,  ground  glass  stoppers.  To  be  labeled 
as  desired,  with  paper  labels. 

For  this  purpose  secure  one  or  two  label  books  (.70).  The 
labels  should  be  pasted  carefully  so  that  the  paper  will  not 
"pucker  up",  the  "gum"  allowed  to  dry  thoroughly,  and  then 
a  layer  of  melted  paraffin  spread  with  a  brush  over  the  label, 
beyond  the  edges. 

The  salt  mouth  bottles  for  the  general  supply  shelf  probably 
need  not  be  purchased  separately,  as  the  bottles  in  which  salts 
are  shipped  serve  well  for  this  purpose. 

Balances  for  ordinary  weighing,  capacity  1000  grams.  A  very 
desirable  balance  is  the  Laboratory  Balance,  Cat.  No.  L  6010 
(list  price,  $12.00),  manufactured  by  Wm.  Gaertner  &  Co., 
5345  Lake  Ave.,  Chicago.  One  such  balance  will  suffice  for  10 
students. 

1  set  of  weights,  third  class,  10  grams  up  to  2  Kg.  (This  bal- 
ance has  a  sliding  weight  for  .the  smaller  weight  down  to  0.1 
gram). 

Water  Still.  If  running  water  is  at  hand,  a  small  automatic 
still  (for  instance,  a  J&well]  should  be  installed  (one  of  capac- 
ity %  gallon  per  hour  will  be  ample  for  10  to  20  students).  If 
the  laboratory  is  not  supplied  with  gas,  a  small  (1  hole)  blue- 
flame  kerosene  stove  should  be  bought,  and  placed  in  position  to 
heat  the  still.  If  running  water  is  not  available  in  the  laboratory, 
a  (5  gallon)  copper  retort  (tin  lined)  and  a  block  tin  worm  con- 
denser may  be  used.  It  can  be  heated  with  a  Fletcher  radial  gas 
burner  or  with  a  kerosene  blue-flame  stove.  Either  distilling 
apparatus  will  cost  slightly  above  $20.00.  Two  5  gallon  stout 


30  University  of  Texas  Bulletin 

glass  bottles  for  collecting  and  storing  distilled  water  should  be 
secured  ($3.00),  and  one  of  them  should  be  fitted  with  a  glass 
syphon  and  pinch  cock  for  drawing  the  water. 

Two  Acid  Pots,  stone  ware,  3  gallons  capacity,  for  dilut- 
ing acids $2.00 

3  Sets  of  3  smallest  sizes  of  cork  borers 1.50 

1  Set  of  6  smallest  sizes  of  cork  borers 80 

3  Kipps  automatic  gas  generators,  capacity  1  pt.,  with 
a  broad  base  having  a  " tubular"  in  it  for  emptying 
the  spent  acid.  For  convenience  in  ' '  filling, ' '  the  tubu- 
lar in  the  middle  "globe"  should  be  of  3^2  cm.  inner 

diameter    9.00 

100  ft.  Tubing  of  soft  glass,  for  bending,  etc.,  diam.  9%x 

121/2  mm 85 

30  ft.  Tubing  of  soft  glass,  for  bending,  etc.,  diam.  14x18     .50 
100  ft.  Tubing  of  soft  glass,  for  bending,  etc.,  5mm.  outer 

diam 42 

100  ft.  Tubing  of  soft  glass,  for  bending,  etc.,  diam.  6x4. ..  .50 
100  ft.  Tubing  of  soft  glass,  for  bending,  etc.,  diam.  7x5. .  .  .45 

30  ft.  soft  glass  rodding,  3  mm.  diameter 15 

10  ft.  soft  glass  rodding,  6  mm.  diameter 10 

6  Thermometers,  solid  stem,  graduated  up  to  360°  C 7.50 

12  Calcium  Chloride  U-tubes,  6  in.  with  side  tubes  at- 
tached   72 

12   Mohr 's   pinchcock   clamps 98 

12  Screw  clamps  for  compressing  rubber  tubing 3.00 

6  Lead  dishes,  3  inches  in  diameter .75 

12  Distilling  flasks,  350  to  400  cc.  with  effluent  tube  half- 
way up  the  neck.  They  are  to  be  used  in  place  of  re- 
torts. For  a  condenser,  use  a  piece  of  soft  glass  tubing 
diameters  10x13  mm.  Fit  this  over  the  side  tube  of  the 
distilling  flask  by  wrapping  a  strip  of  asbestos  around 
the  latter.  When  necessary  place  a  wet  towel  around 
the  condensing  tube,  or  let  this  extend  into  a  receiving 
flask  submerged  in  water.  To  apply  heat,  place  the  dis- 
tilling flask  over  a  hole  (1%  to  2  inches  diameter)  in  a 
piece  of  asbestos  board  which  is  5x5  inches  in  size. 
This  prevents  the  flame  from  striking  portions  of  the 
flask  above  the  level  of  the  liquid  in  it 1.50 


Chemistry  in  High  Schools  31 

2  Large  porcelain  spoons 50 

1  Measuring  cylinder,  1000  cc.  open  top 50 

4  Volumetric  flasks  without  glass  stoppers: 

1_1000  cc 35 

1—  500  cc 25 

1—  250  cc 20 

1—  100  cc 16 

1  Measuring  cylinder,  1000  cc.  glass  stoppered 63 

2  10  cc.  Pipettes 10 

2  25  cc.  Pipettes 14 

2  Glass  funnels,  6  inches  diameter • . . .     .40 

4  Porcelain  evaporating  dishes,  ordinary  form : 

1 — 5  inch  diam 20 

1—6  inch  diam 23 

1 — 7  inch  diam 30 

1—8  inch  diam 38 

2  Large  porous  cups  and  1  rubber  stopper  to  fit  these — to 
be  used  for  the  demonstration  of  gaseous  diffusion.    A 
bell  jar  can  probably  be  borrowed  from  the  physical 
laboratory  for  this  purpose. 
Beakers  of  best  Bohemian  glass : 

3  nests  each,  about  600  cc.,  800  cc.  and  1000  cc 1.80 

1  Package  of  100  circular  filter  papers,  12  inch  diam 16 

1  Glass  tube  cutter   (inside  cutter)   with  extra  cutting 

wheels.     (E.  &' A.  Cat.  3684) 1.25 

1  filter  Pump  (Aspirator),  of  brass,  medium  size 1.50 

"Picein"  rubber  cement,  very  convenient  and  useful  for 
tightening  joints  and  stoppers  in  apparatus.    It  is  applied 
like  sealing  wax,  but  is  preferable  to  the  latter.    Dealers 
can  secure  same  from  Fritz  Koehler,  Leipzig,  Germany,  4 

pieces  at  15  cents  apiece,  approximately 60 

Cork  stoppers,  best  quality — regular  size. 
Diam.  Small  End. 

100 14 38 

"    16 50 

"    18 60 

"    20 1.00 

50... 22 55 

..24..  .60 


32  University  of  Texas  Bulletin 

".., 26 65 

" 28 75 

" 30 1.00 

il 32 1.10 

Rubber  Tubing.  Besides  that  necessary  for  the  Bunsen  burn- 
ers and  the  black  rubber  tubing  in  the  individual  outfits,  "for 
connections, ' '  secure  the  following : 

Rubber  tubing,  white,  best  quality,  wrapped  in  cloth, 
Amount  Diam. 

20  ft.  13x  7  mm $3.60 

10  ft.  15x11  mm 3.00 

Special  Apparatus  for  Quantitative  Experiments. 

Balance  for  quantitative  work.  This  should  be  a  balance  in  a 
glass  case  sensitive  to  a  milligram.  The  capacity  of  the  balance 
should  be  300  grams,  and  a  set  of  second  (not  third)  class  weights 
should  be  provided  for  it,  and  a  supply  of  extra  fractional 
weights  should  be  on  hand  to  replace  any  that  may  be  lost.  The 
balance  shown  in  Eimer  end  Amend 's  catalogue  No.  2122,  and 
the  set  of  weights  No.  2198  (200  grams)  are  suitable  for  this 
purpose.  In  general,  one  such  balance  will.be  enough  for  seven 
or  eight  students  only,  hence  if  much  of  this  work  is  to  be  done, 
two  such  balances  should  be  provided  for  a  class  of  twelve  stu- 
dents. The  price  of  such  a  balance  and  weights  is  about  $20.00 
to  $25.00. 

12  Porcelain  combustion  boats,  7x70  mm.  or  10x60  mm. 

Apparatus  for  the  Section  on  Electrolysis,  lonisation,  etc. 

See  special  section  on  electrolysis  and  battery  action.  The 
following  will  be  needed : 

12  Porous  cups,  height  3  inches,  diameter,  1%.  They  should 
be  well  protected  against  dust. 

12  Rubber  stoppers  to  fit  these.  Holes  can  be  cut  in  them  as 
needed.  This  is  easily  done  by  means  of  the  ordinary  cork 
borer  if  it  is  moistened  with  sodium  hydroxide  solution  or  with 
alcohol . 

1  Drying  Tower  (E.  &  A.  Cat.  N.  3055),  18  inches  high.  .$  .50 
12  small  carbon  rods — i.  e.  arc  light  electrodes — can  be  secured 

locally. 


Chemistry  in  High  Schools  33 

4  Plantinum  electrodes  each  consisting  of  a  thin  piece  of 
platinum  foil  2x5  cm.  to  one  end  of  which  is  welded  a 
short  piece  of  No.  22  platinum  wire.    The  latter  is  fused 
into  a  four-inch  piece  of  strong  glass  tubing  (extending  to 
the  inside),  having  7  mm.  outer  diameter,  and  for  elec- 
trical connection,   a  little  mercury  is  poured  into  the 
tube $5.00 

2  Porcelain  jars,  with  diameter  6"  to  8,"  height  4"  to  6" 

can  be  secured  at  a  local  dealer 40 

Ammeter,  voltmeter,  rheostat,  etc.,  may  probably  be  bor- 
rowed temporarily  from  the  physical  laboratory.  If  not, 
then  at  least  one  ammeter  with  two  ranges  (1  amp.  and  10 
amp.)  and  one  voltmeter  with  two  ranges  (3  volts  and  30 
volts)  should  be  bought.  These  instruments  should  be  of 
fairly  good  grade,  hence  they  should  cost  at  least  $15.00 
a  piece. 

1  Piece  fairly  stiff  sheet  copper  (about  the  thickness  used 
in  lining  bath  tubs)  16x16  inches 50 

1  Wooden  "Conductivity"  vessel  made  to  order  (see  page 
77  2.50 

y2  lb.  Picric  acid 75 

1/2  lb  Naphthalene  c.  p 25 

1  Liter  absolute  alcohol 35 

Apparatus  for  the  Demonstration  of  Combining  Volumes  of  Gases 

1  Hoffman  Electrolysis  apparatus ;  for  details  see  page  53 .  $6.00 
1  Eudiometer  Tube  of  special  design  (see  page  53)  for  the 

explosion  of  hydrogen  and  oxygen 5.00 

1  Hoffman  apparatus  tube  to  demonstrate  the  volume  re- 
lations for.  ammonia — this  tube  to  be  modified  as  stated  on 
page  55 3.00 

Chemicals  for  a  Cla\ss  of  Twelve  Students. 

5  Ibs.  Acetic  Acid  glacial $1.02 

18  Ibs.  Hydrochloric  Acid  c.  p.  in  6  lb.  sealed  bottles 2.16 

7  Ibs.  Nitric  Acid,  c.  p.  in  7  lb.  sealed  bottles 1.00 

2  Ibs.  Fuming  Nitric  Acid ,   1.10 


34  .         University  of  Texas  Bulletin 

1  Ib.  Oxalic  Acid,  commercial 12 

27  Ibs.  Sulphuric  Acid,  c.  p.  in  9  Ib.  sealed  bottles 2.85 

1  Ib.  Tartaric  Acid 64 

2  qt.  95%  Alcohol 50 

1  Ib.   Ammonium   Carbonate 25 

^4  Ib.  Ammonium  Oxalate 12 

1  Ib.  Potassic  Alum 08 

%  Ib.  Aluminium,  filings  or  shavings 35 

5  Ibs.  Ammonium  Chloride,  pure 90 

1A  Ib.  Ammonium  Sulphate 10 

16  Ibs.  Ammonium  Hydroxide  in  4  Ib  bottles 2.80 

3  Ibs.  Ammonium   Nitrate 70 

8  ozs.  Antimony,  powdered 25 

4  ozs.  Arsenic  Trioxide 13 

Y2  Ib.  Asbestos  wool 20 

1  sq.  yd.  Thin  Asbestos  paper 10 

2  Ibs.  Barium   Chloride,  crystals .25 

*4  Ib.  Barium  Nitrate *. 10 

%  Ib-  Barium  Peroxide 35 

1  oz.   Bismuth 30 

1  Ib.  Borax 18 

%  Ib.  Bromine  in  2  oz.  bottles 50 

1  Ib.  Calcium    Chloride,   crystals 35 

2  Ib.  Calcium  Chloride,  anhydrous,  fused 80 

1  Ib.   Cadmium   Chloride 1.3-6 

1  Ib.  Calcium  Fluoride 10 

Calcium  oxide,  buy  locally 

*4  Ib.  Cadmium   Nitrate 40 

1  Ib.  Calcium  Nitrate 80 

%  Ib.  Chrome  Alum,  c.  p 25 

1  Ib.  Chloroform,  Squibb's 90 

5  Ibs.  Calcium  Sulphate,  Plaster  of  Paris 15 

1  Ib.  Carbon   Bisulphide '. 16 

10  Ibs.  Calcium  Carbonate,  marble  chips 50 

2  Ibs.  Bone  Black 15 

1  oz.   Cobalt  Nitrate 15 

1  doz.  sticks  Willow  Charco:al 36 

1  Ib.  Thin  Copper  Foil 50 

2  Ibs.  Copper  Turnings,  fine 40 


Chemistry  in  High  Schools  35 

2  Ibs.  Copper  Nitrate 65 

1  Ib.  Copper  Oxide,  black  powdered 75 

5  Ibs.  Copper   Sulphate 50 

2  oz.  Iodine,  pure,  crystals 75 

2  Ibs.  Ferrous  Sulphate  in  2  oz.  bottles 40 

1  Ib.  Ferric  Chloride 12 

2  Ibs.  Iron    Filings 10 

5  Ibs.  Iron  Sulphide - 35 

2  Ibs.  Sheet  Lead .-. . . .20 

1  Ib.  Lead   Nitrate 18 

1  Ib.  Litharge   12 

1  Ib.  Lead   Peroxide 36 

1  oz.  Litmus    10 

1  Quire  Litmus  paper,  red 50 

1  Quire  Litmus  paper,  blue 50 

2  ozs.  Magnesium  ribbon 1.20 

1  Ib.  Magnesium  Chloride 12 

1  Ib.  Manganese   Chloride 50 

2  Ibs.  Manganese  Dioxide,  powdered 85 

3  Ibs.  Manganese  Dioxide,  in  lumps 1.00 

5  Ibs.   Mercury 4.00 

4  Ib.  Mercuric   Chloride 40 

8  ozs.  Red  Oxide  of  Mercury 80 

±  Ib.  Mercurous  Nitrate 40 

1  Ib.  Nickel  Chloride 70 

1  oz.  Phenolphthalein    10 

5  Ibs.  Paraffin 75 

1  oz.  Red  Phosphorus 15 

±  Ib.  Yellow   Phosphorus 25 

±  oz.  Potassium 45 

1  Ib.  Potassium  Bromide 20 

2  Ibs.  Potassium  Hydroxide,  sticks 60 

1  Ib.  Potassium  Carbonate 16 

5  Ibs.  Potassium  Chlorate,  crystals 70 

1  Ib.  Antimony  :and  Potassium  Tartrate 60 

2  Ibs.  Potassium  Bichromate 32 

Ib.  Potassium  Ferrocyanide 30 


36  University  of  Texas  Bulletin 

1/2  lb.  Potassium  Ferricyanide 30 

V2  lb.  Potassium  Iodide  2.40 

1  lb.  Potassium  Nitrate 15 

%  lb.  Potassium  Sulphocyanate 15 

3  Ibs.  Potassium  Chloride 25 

1/2  lb.  Potassium  Permanganate 10 

1  oz.  Platinized  Asbestos 5.00 

y2  oz.  Silver  foil 60 

1/2  lb.  Silver  nitrate 4.00 

8  oz.  Sodium '. 70 

2  Ibs.  Sodium  carbonate  crystals 25 

3  Ibs.  Caustic  soda,  sticks 75 

2  Ibs.  Sodium  chloride,  c.  p 50 

%  lb.  Sodium  chlorate 10 

3  Ibs.  Sodium  nitrate 42 

2  Ibs.  Sodium  sulphate,  crystals 25 

1  lb.  Sodium,  sulphide,  crystals 10 

2  Ibs.  Sodium  hyposulphite 15 

1  lb.  Sodium  phosphate 4 ;10 

2  Ibs.   Sodium  bisulphite 60 

1/2  lb.   Sodium  acetate •. 25 

1  lb.  Sodium  peroxide,  commercial 70 

1/2  lb.  Stannous  chloride 25 

1  oz.  Strontium  chloride 10 

5  Ibs.  Boll  sulphur 25 

1  lb.  Flowers  of  Sulphur 08 

3  Ibs.   Granulated  zinc 45 

3  lb.  Zinc  in  sticks,  at  least  6  in.  in  length 25 

5  Ibs.  Zinc  in  lumps  or  short,  thick  rods,  1  in.  long,  "for 

Kipps"    1.25 

1  lb.  Zinc  sulphate 25 

y2  lb.  Zinc  nitrate 50 

1  lb.  Granulated  tin .55 

2  ozs.  Glass  wool,  fine 1.00 

Cost  of  Supplies. 

The  prices  given  in  the  list  of  "Individual  Supplies"  are  those 
that  would  be  charged  at  Austin,  hence  they  include  freight. 


Chemistry  in  High  Schools  37 

The  prices  for  the  other  supplies  are  to  serve  as  indications 
merely;  they  have  not  been  obtained  by  special  quotation  from  a 
firm;  and  they  do  not  include  freight.  For  the  latter  about  10 
to  15%  must  be  added  to  the  price. 

The  total  cost  of  the  supplies  in  this  list,  figured  for  a  teacher 
and  twelve  students,  and  including  freight  is : 

Individual  Sets $182.96 

General   Supplies 53.75 

Freight  and  Drayage,  l2l/2%  on  the  latter 6.50 

Total   $243.21 

First  Cost  of  Laboratory. 

If  all  furniture  is  constructed  as  cheaply  as  possible,  its  cost 
will  be  approximately  as  follows : 

12  lockers,  for  students,  including  plumbing $  75.00 

Reagent  side  shelves,  shelves  in  store  room,  work  table  for 

teacher,  and  large  sink 50.00 

One  draft  hood '. 25.00 

Chemical  supplies 250.00 

Total    $400.00 

Cost  of  Maintenance. 

The  least  annual  cost  of  maintenance  is  about  $8.00  to  $12.00 
per  student.  Of  this  amount  from  $2.50  to  $5.00  may  be  borne 
by  the  student,  and  the  remainder  by  the  Board.  In  many  Texas 
High  Schools,  the  Board's  appropriation  is  as  much  as  $10.00 
per  student  annually. 


38  University  of  Texas  Bulletin 


PART  II:  PLAN  AND  CONDUCT  OF  THE  COURSE. 

Main  Object  of  Course. 

The  question  to  be  considered  here  is :  for  which  set  of  students 
shall  the  course  be  designed — those  who  end  their  school  days 
with  the  high  school,  or  those  who  go  to  college?  The  writer 
believes  that  the  course  should  be  designed  primarily  for  the 
student  who  will  not  continue  his  studies  beyond  the  high  school ; 
and  the  following  plan  and  suggestions  have  been  made  with  that 
in  view.  Furthermore,  the  writer  believes  that  such  a  course  will 
also  be  the  best  introduction  to  the  subject  for  the  student  who 
continues  the  study  of  chemistry  in  college. 

For  this  purpose  the  course  should  consist  mainly  of  a  presen- 
tation of  experimental  facts  connected  by  the  least  amount  of 
theory  necessary  to  aid  in  their  study.  Emphasis  should  con- 
stantly be  given  to  the  recognition  and  retention  of  the  experi- 
mental facts  themselves.  Furthermore  an  essential  part  of  the 
course  should  deal  with  facts  with  which  the  student  will  be  con- 
cerned later  in  life. 

Which  first,  Chemistry  or  Physics? 

The  question  whether  chemistry  or  physics  shall  precede  in  the 
high  school  course  is  a  matter  that  should  be  left  entirely  to  the 
high  school  people.  Read  in  this  connection,  The  Teaching  of 
Chemistry  and  Physics,  pages  29  to  37.  Attention  should  be 
called  to  the  fact  that  the  progress  of  the  class  will  naturally  be 
slower  if  chemistry  is  given  earlier  in  the  course  than  if  it  is  given 
during  the  last  year.  Furthermore,  one  topic  must  be  given  special 
consideration,  that  is  the  topic  of  battery  cells  and  electrolysis. 
This  subject  should  be  given  in  the  chemistry  course  rather  than 
in  the  physics  course  because  it  is  essentially  a  chemical  subject. 
It  cannot  be  presented  without  involving  chemical  considerations, 
and -elementary  chemistry  cannot  be  presented  properly  without 
it  (see  page  81  et.  seq.). 

Time  Allowance  for  the  Course. 

The  time  given  to  chemistry  in  the  high  school  should  be  three 
recitation  periods  of  45  minutes  and  two  laboratory  periods  of  at 


Chemistry  in  High  Schools  39 

least  double  that  time  a  week.  Each  double  period  for  laboratory- 
work  should  be  uninterrupted,  that  is,  there  should  be  two  con- 
secutive periods.  There  should  be  no  difficulty  in  arranging  the 
schedule  for  this,  because  a  study  period  may  be  placed  just  be- 
fore or  after  the  recitation  period,  and  on  days  on  which  labora- 
tory work  is  taken,  the  recitation  period  together  with  the  study 
period  then  form  the  laboratory  period.  This  arrangement  is 
desirable  for  another  reason :  it  frequently  happens  that  the  ra- 
tio between  laboratory  and  recitation  work  temporarily  should 
be  changed  in  either  way  possible,  because  at  times  the  recita- 
tion work  requires  more  attention  and  at  others  the  laboratory 
work.  The  arrangement  of  the  schedule  here  suggested  permits 
of  such  a  change,  and  hence  is  highly  desirable. 

Time   Allowance   for  Preparation  of  Laboratory   and  Lecture 
Table  Experiments. 

\ 

Considerable  time  must  be  spent  by  the  teacher  in  the  prepara- 
tion of  special  apparatus,  in  the  preparations  of  solutions  for  the 
laboratory,  and  in  the  preparation  of  lecture  table  experiments. 
In  addition  to  this  there  is  the  unavoidable  labor  of  putting  away 
the  apparatus  properly  after  use,  and  arranging  the  side  shelf 
reagents,  etc.,  after  periods  of  laboratory  work.  As  a  rule  su- 
perintendents and  principals  either  do  not  realize  how  time  con- 
suming this  work  is  or  they  are  disposed  to  minimize  its  impor- 
tance. Some  will  consider  that  this  is  essentially  janitorial  work, 
for  which  some  cheap  help  might  either  be  hired,  or  which  if 
done  by  the  teacher  does  not  deserve  any  consideration  as  a 
part  of  his  teaching  work.  This  is  utterly  wrong.  The  teacher 
of  chemistry  should  be  allowed  time  enough  to  do  such  work 
properly,  and  such  time  should  be  a  part  of  his  teaching  time, 
and  not  of  hours  after  school  work.  If  the  suggestion  made  above 
for  the  scheduling  of  the  laboratory  and  of  the  recitation  work  is 
followed,  then  in  addition  to  the  double  period  each  day,  kept 
open  throughout  the  week  for  chemistry,  there  should  be  set  aside 
another  period  each  day  for  the  teacher  to  look  after  the  equip- 
ment. In  this  way  he  will  have  two  periods  three  times  a  week 
and  one  period  twice  a  week,  a  total  of  eight  periods  to  prepare 
his  experimental  work.  This  is  not  excessive  and  will  be  very 
profitable  to  the  school.  If  classes  are  large,  the  teacher  must  be 


40.  University  of  Texas  Bulletin 

given,  in  addition,  assistants  to  aid  him  in  cleaning  up  the  lab- 
oratory, etc.  Such  service  can  be  secured  very  reasonably  from 
some  member  of  the  chemistry  class.  The  cleaning  up  should  not 
be  done  without  the  direction  of  the  teacher,  because  he  should 
know  where  everything  is  placed. 

However,  such  time  allowance,  etc.,  puts  a  responsibility  upon 
the  teacher  which  he  must  not  shirk.  A  chemistry  teacher  must 
be  "up  and  about"  doing  experimental  work  with  his  own  hands. 
All  "sitting  back"  and  letting  the  students  only  do  experimental 
work  or  ordering  around  some  assistant  to  prepare  experiments 
and  reagents  is  indictative  of  a  person  unfit  to  be  a  teacher  of 
science.  He  must  be  the  chief  experimenter;  he  must  be  pos- 
sessed of  a  desire  to  do  experimental  work,  and  with  his  own 
hands  attend  to  matters  in  the  laboratory. 

Manner  of  Conducting  laboratory  Work. 

Beginners  in  chemistry  are  frequently  inclined  to  do  their 
laboratory  work  in  a  mechanical  manner  merely,  and  the  new- 
ness of  the  subject  inclines  them  also  to  take  too  much  time  in 
the  performance  of  experiments.  Hence  the  teacher  must  use  a 
method  of  conducting  laboratory  work  which  will  keep  the 
mental  aspect  of  the  subject  constantly  before  them  and  force 
them  to  do  their  work  expeditiously.  This  may  be  done  by  con- 
ducting the  laboratory  work  in  a  manner  similar  to  that  of  con- 
ducting class  work.  Thus  at  suitable  times  during  the  periods 
of  laboratory  work,  the  teacher  should  discuss  with  the  whole  class 
the  chemical  changes  dealt  with,  and  drill  his  pupils  on  all  re- 
lated matter.  He  should  strive  by  all  means  possible  to  enliven 
the  activity  of  laboratory  practice,  realizing  that  it  is  in  the  lab- 
oratory rather  than  in  the  lecture  room  that  chemistry  may  be 
taught  and  learned. 

In  the  treatment  of  the  experimental  material  the  aim  should 
be  to  teach  the  common  properties  of  substances  in  the  broadest 
manner.  Thus  in  connection  with  the  preparation  of  oxygen, 
the  student  should  not  be  taught  that  "the  laboratory  method 
for  the  preparation  of  oxygen  consists  of  heating  a  mixture  of 
potassium  chlorate  and  manganese  dioxide,"  but  he  should  be 
taught  that  "there  are  some  compounds  of  oxygen  that  decom- 
pose when  exposed  to  a  sufficiently  high  temperature  and  yield 


Chemistry  in  High  Schools  41 

• 

oxygen  as  one  of  the  products  of  decomposition.  Of  course  not 
all  substances  break  up  in  the  temperatures  at  our  command,  yet 
quite  a  number  do  so,  among  which  may  be  mentioned  lead 
peroxide,  mercuric  oxide,  potassium  chlorate,  potassium  nitrate, 
etc.  These  should  be  remembered  as  substances  not  only  rich  in 
oxygen  but  that  yield  it  up  when  exposed  to  a  moderately  high 
temperature  obtainable  in  the  laboratory."  By  this  means  the 
student  has  not  only  learned  how  oxygen  may  be  prepared,  but 
he  has  learned  to  some  extent  the  behavior  of  oxygen  compounds 
exposed  to  different  temperatures.  The  information  thus  con- 
veyed is  farther  reaching  and  more  general  than  the  mere  prep- 
aration of  oxygen.  This  effort  to  teach  something  of  general 
bearing  in  connection  with  the  specific  information  conveyed 
should  be  made  wherever  it  is  possible.  In  the  Outline  for  a 
Course  which  is  given  farther  on  in  this  paper,  this  principle  is 
applied  rather  carefully,  as  may  be  noticed  by  looking  at  the  first 
few  topics  given. 

In  the  teaching  of  experimental  work  it  should  be  empha- 
sized that  an  experiment  is  valuable  only  if  it  is  clearly  remem- 
bered by  the  student.  There  exists  a  mistaken  notion  that  ex- 
perimental work  is  intended  primarily  to  train  the  student  in 
the  performance  of  such  work  somewhat  for  the  same  reason 
that  training  is  necessary  in  carpenter  work,  metal  work,  etc. 
Such  training  is  only  an  incidental  object  which  is  attained 
without  particular  effort  if  the  work  is  done  properly.  The 
main  object  is  to  learn  something  about  the  substances,  and  the 
whole  value  of  the  work  is  lost  if  the  experiment  is  forgotten. 
It  is  practically  true  that  the  value  of  the  course  is  propor- 
tional to  the  accuracy  with  which  everything,  including  details 
of  a  set  of  well  selected  experiments,  is  remembered. 

Note  on  Quantitative  Experiments. 

Although  quantitative  experiments  are  usually  introduced 
early  in  the  course,  yet  it  appears  to  the  writer  that  it  is  in- 
advisable to  do  so.  It  is  only  when  the  student  has  a  fairly 
extensive  knowledge  of  chemical  phenomena  that  he  can  appre- 
ciate quantitative  relations.  However,  later  in  the  course  quan- 
titative experiments  are  extremely  valuable.  In  this  connec- 
tion see  page  52. 


42  University  of  Texas  Bulletin 

• 
The  Note  Book. 

The  first  thing  to  insist  upon  in  the  note  books  is  correct 
spelling  and  correct  composition. 

Next,  all  attempts  to  use  blanks,  to  be  filled  in,  or  detailed 
"patterns,"  to  be  followed  for  the  writing  up  of  experiments, 
are  to  be  discouraged.  A  few  general  directions  are  naturally 
necessary,  but  any  approach  to  a  "formula"  to  be  used  in  writ- 
ing up  experiments  should  be  decidedly  discouraged. 

The  first  general  direction  given  to  students  for  writing  up 
their  notes  is  to  call  attention  to  the  fact  that  the  name  of  the 
book  should  be  indicative  of  its  use;  it  should  be  a  note  book, 
and  not  a  re-written  text  book  or  a  book  of  essays.  If  in  per- 
forming the  experiments,  printed  directions  have  been  fol- 
lowed, then  these  directions  should  not  be  copied  into  the  note 
book.  Of  course  such  directions  should  be  definitely  referred 
to  in  some  such  manner  as  this:  "Experiment  (number) 
-  page  —  -  in  Smith's  Laboratory  Manual  was 

performed  in  full  (or  "with  the  following  exceptions").  If 
additional  experiments  in  which  printed  directions  were  not 
followed  have  been  performed  by  the  student,  then  these  may 
be  written  out  in  full. 

In  the  note  book  the  experiments  may  be  numbered  merely 
for  the  sake  of  indicating  the  order.  However,  the  most  im- 
portant thing  is  to  devise  for  each  experiment  a  heading  which 
states  clearly  the  nature  and  object  of  the  experiment.  Con- 
siderable time  may  be  spent  in  thought  in  order  to  devise  head- 
ings that  may  be  properly  significant.  A  suitable  heading  is 
just  :as  important  in  itself  as  all  the  notes  that  follow,  and  the 
devising  of  proper  headings  is  one  of  the  best  means  to  force 
the  student  to  realize  what  he  is  doing  and  what  he  is  doing  it 
for.  The  heading  should  not  be  merely  a  general  term,  •  and 
not  more  than  one  definite  subject  should  be  put  under  it. 
Thus  it  is  absurd  to  give  the  heading  "oxygen"  to  all  the  ex- 
periments given  in  connection  with  the  study  of  that  subject. 
Some  of  the  experiments  in  connection  with  oxygen  have  been 
made  with  the  view  of  demonstrating  with  what  chemicals  and 
with  what  operations  it  may  be  prepared.  Other  experiments 
may  have  been  made  with  the  view  of  preparing  certain  bottles 


Chemistry  in  High  Schools  43 

f  ul  of  the  gas  and  showing  some  of  its  common  properties.  Hence 
it  would  be  logical  to  head  one  experiment  as  follows:  "To 
demonstrate  with  what  substances  and  what  operation  oxygen 
may  be  prepared."  The  other  experiment  should  be  headed 
somewhat  as  follows:  "The  preparation  and  collection  of 
oxygen  gas  and  the  demonstration  of  some  of  its  properties. ' ' 

The  assignment  of  separate  headings  to  distinct  parts  of  ex- 
perimental work  should  not  be  carried  to  the  extreme.  It  is 
unnecessary  to  divide  the  last  experiment  discussed  above  into 
the  following:  first,  the  preparation  and  collection  of  the  gas; 
second,  the  combustion  of  sulphur  in  oxygen,  etc.  The  collec- 
tion of  several  operations  under  one  heading  naturally  requires 
thought,  and  during  the  first  part  of  the  course  the  student  will 
have  much  difficulty  with  it,  but  the  benefit  gained  both  as  far 
as  grasping  the  subject  is  concerned  and  as  far  as  training  in 
composition  is  concerned  will  amply  repay  the  time  spent  upon 
this  work. 

In  the  body  of  the  "write  up"  the  first  thing  to  be  given  is 
a  direct  reference  to  the  directions  followed,  e.  g. :  Smith, 
Exp.  -  — ,  page  -  — ,  was  performed  in  full"  (or 

with  the  following  exceptions"),  etc. 

Then  should  follow  a  brief  definite  statement  of  what  was 
actually  noted  or  observed,  which  has  not  been  given  in  the 
printed  directions  referred  to  above.  For  example,  under  the 
last  heading  mentioned  would  appear:  sulphur,  carbon,  phos- 
phorus and  sodium  after  they  were  heated  to  their  kindling 
temperatures  burned  vigorously  in  the  oxygen  gas.  The  prod- 
uct of  combustion  of  carbon  (carbon  dioxide)  is  an  invisible, 
inodorous  gas;  that  of  sulphur  is  an  invisible  gas  with  suffocat- 
ing odor;  that  of  phosphorus  is  a  white  solid  and  that  of  so- 
dium is  a  white  solid.  Treated  with  water,  these  substances 
give  solutions  the  first  three  of  which  turned  blue  litmus  red 
and  the  last  turned  red  litmus  blue.  The  equations  for  the 
chemical  actions  which  take  place  during  combustion  and  after- 
wards on  treatment  of  water  are  as  follows:  " 

The  notes  should  always  show  the  equations  of  the  reactions 
in  the  experiment.  Care  must  be  taken  by  the  teacher  to  see 
that  they  are  written  correctly. 


44  University  of  Texas  Bulletin 

How  to  Begin  the  Course. 

Avoid  beginning  by  giving  definitions,  for  instance  of  ele- 
ments, compounds,  chemistry,  atoms,  molecules,  etc.  Starting 
with  definitions  reverses  the  attitude  of  the  student  towards 
the  subject  matter,  and  is  really  contrary  to  the  natural  method 
of  learning  a  new  subject.  We  teach  a  child  a  certain  thing  by 
mentioning  its  name  and  showing  the  thing,  and  perhaps  speak- 
ing about  it.  This  should  be  the  mode  of  procedure  in  the  in- 
troduction of  this  subject,  which  presents  entirely  new  things 
to  the  student.  Without  attempting  an  explanation,  the  teacher 
should  bring  before  the  student  the  preparation  and  properties 
of  several  elements,  oxygen,  hydrogen,  chlorine,  etc.,  and  tell 
him  that  these  are  elements.  The  formation  of  compounds,  the 
various  indications  that  chemical  changes  take  place,  are  all 
shown  incidentally  in  connection  with  these  examples,  and  after 
a  little  while  the  student  will  be  in  position  to  form  a  definite 
notion  as  to  what  the  terms,  elements,  compounds,  chemical  ac- 
tions, etc.,  mean.  The  attempt  to  introduce  the  fundamental 
terms  abstractly  at  the  very  beginning  of  the  subject  consumes 
a  great  deal  of  time  and  is  rather  unprofitable. 

Introductory  chapters  concerning  experimental  examples  of 
chemical  change,  the  influence  of  heat,  what  is  meant  by  a  solu- 
tion, exercises  in  weighing,  measuring,  etc.,  are  also  of  ques- 
tionable value.  .  At  best  they  are  rather  unfruitful  and  cer- 
tainly uninteresting  to  the  student.  At  the  University  of  Texas 
they  are  omitted  altogeher,  and  the  first  exercise  given  is  the 
study  of  the  preparation  of  oxygen. 

The  Introduction  of  Symbols  and  of  the  Notions  of  Atoms  and 

Molecules. 

It  is  a  mistake  to  speak  constantly  about  atoms  and  molec- 
ules and  treat  them  as  something  absolutely  essential  to 
chemistry.  Students  are  naturally  inclined  to  consider  that 
atoms  and  molecules  are  the  main  things  with  which  chemistry 
deals,  hence  a  particular  effort  must  be  made  against  this  in- 
clination. Emphasize,  at  the  beginning,  that  chemistry  deals 
with  facts,  with  things  in  this  world  as  they  are,  and  that  the 


Chemistry  in  High  Schools  45 

notion  of  atoms  and  molecules  is  introduced  merely  for  the 
purpose  of  forming  a  simple  mental  picture. 

It  is  highly  desirable  to  use  chemical  symbols  and  formulae 
as  early  and  as  extensively  as  possible.  However,  these  are  not 
necessarily  dependent  upon  any  notion  of  the  existence  of 
atoms  and  molecules.  They  are  mere  short-hand  expressions 
for  the  relations  of  the  weights  of  substances  which  undergo 
chemical  changes  (which  relations  are  merely  the  results  of 
quantitative  experiments).  When  it  has  been  determined  that 
108  parts  by  weight  of  mercuric  oxide  give  100  parts  by  weight 
of  mercury,  and  8  parts  by  weight  of  oxygen,  then  instead  of 
stating  this  fact  in  the  way  that  it  was  just  stated,  chemists 
state  it  by  writing 

HgO=Hg+0 

and  the  student  need  only  be  told  that  this  is  a  special  short- 
hand system  devised  to  represent  or  express  the  proportions  of 
these  substances,  the  symbols  standing  for  certain  numbers 
selected  partly  with  an  eye  to  simplicity  or  convenience.  The 
symbols  need  not  mean  anything  else,  and  this  is  their  funda- 
mental meaning  and  main  use.  Used  in  this  simple  sense,  and 
for  this  definite  purpose,  symbols  and  equations  should  be  in- 
troduced from  the  very  beginning,  and  the  fundamental  (quan- 
titative) significance  should  be  constantly  referred  to  by  the 
teacher. 

After  some  seven  or  eight  chapters  dealing  with  different 
kinds  of  chemical  substances  have  been  studied,  then  the 
teacher  may  point  out  briefly  (1)  that  we  imagine  any  one  ele- 
ment made  up  of  distinct  little  pieces  all  of  the  same  weight 
(atoms),  which  weights  show  the  same  relation  as  the  num- 
bers represented  by  their  symbols,  and  (2)  that  compounds  are 
merely  collections  of  clusters  of  the  atoms  of  elements  in  such 
bunches  as  are  indicated  by  the  formulae  of  compounds.  With 
this  the  student  has  been  told  all  that  he  need  be  told  for  the 
present  about  the  atomic  and  molecular  structure  of  matter. 
All  attempts  to  show  how  the  atomic  weight  table  was  derived, 
all  attempts  to  show  that  the  atomic  hypothesis  rests  upon  the 
laws  of  definite  and  of  multiple  proportion  will  necessarily  be 
philosophical,  and  it  is  questionable  whether  such  attempts  can 
be  made  profitably  at  this  time.  (In  this  connection  see  page  52.) 


46  University  of  Texas  Bulletin 

Nearly  all  text  books  consider  fairly  early  the  relations 
by  volume  of  combining  gases,  which  naturally  leads  to 
the  presentation  of  Avogadro's  Hypothesis  and  the  determina- 
tion of  molecular  weights.  These  topics  as  constituents  of  the 
first  two-thirds  of  the  high  school  chemistry  course  are  wholly 
undesirable.  They  should  not  be  given  till  later.  If  given 
earJy  they  tend  to  incline  the  student  too  much  toward  the 
theoretical  aspects  of  the  subject,  an  inclination  which  is  alto- 
gether too  great  in  most  young  students. 

However,  toward  the  end  of  the  course  such  topics  may  be 
introduced,  provided  some  of  the  experimental  facts  which 
show  the  relations  by  volume  in  which  gases  combine  are  ac- 
tually presented.  The  emphasis  is  to  be  placed  on  the  presen- 
tation of  the  experiments.  If  the  experiments  are  not  per- 
formed, then  the  whole  topic  should  be  omitted.  In  order  that 
the  teacher  may  not  lose  time  in  selecting  simple,  easily  per- 
formed experiments  for  this  purpose,  a  list  of  suitable  experi- 
ments and  apparatus  is  given  in  this  paper  (see  page  53). 
However,  in  any  case,  the  consideration  given  to  these  topics 
should  not  be  too  great; 

The  Introduction   of   Valence. 

Say  nothing  about  valence  until  several  substances  have  been 
studied.  In  studying  the  first,  few  substances  give  the  stu- 
dents the  formulae  and  equations  and  ask  them  to  memorize 
these  blindly.  State  merely  that  they  are  "short-hand"  ex- 
pressions for  the  relations  of  the  weights  of  the  substances  in- 
volved. Note  where  and  how  valence  is  introduced  in  the 
"Outline  of  the  Course,"  page  66. 

The  Fundamental  Facts  of  Electrolysis  and  Its  Introduction 

in  the   Course. 

Do  not  give  the  electrolysis  of  dilute  sulphuric  acid,  nor  the 
electrolysis  of  any  other  substance  as  examples  of  the  decom- 
position of  these  substances,  and  do  not  attempt  to  show  by 
means  of  the  relation  of  volumes  of  the  gases  obtained  by  elec- 
trolysis that  water  is  composed  of  two  volumes  of  hydrogen  to 


Chemistry  in  High  Schools  47 

one  volume  of  oxygen.  The  first  fundamental  and  most  impor- 
tant fact  concerning  electrolysis  and  the  action  of  batteries  is 
that  the  chemical  actions  at  the  two  poles  are  chemically  in  no 
wise  related.  The  actions  at  the  two  poles  are  also  very  complex 
and  it  is  only  under  special  conditions  that  the  relation  of  the 
volumes  of  the  gases  produced  by  electrolysis  is  just  the  same 
as  that  in  which  they  combine  to  form  water.  The  latter  fact 
can  be  demonstrated  by  showing  that  the  two  gases,  mixed  in 
the  proper  proportion  and  exploded,  combine  completely  to 
form  water,  but  it  does  not  follow  as  a  conclusion  from  the  re- 
sults obtained  by  electrolysis. 

Electrolysis  is  a  complex  subject,  and  should  not  be  treated 
in  the  early  part  of  the  course,  but  should  be  left  to  be  pre- 
sented in  connection  with  other  electrolytic  phenomena  so  that 
the  whole  subject  may  be  clearly  and  connectedly  shown  by  ex- 
periment. An  example  of  a  modern  treatment  of  this  subject 
is  presented  at  length  in  Part  III,  page  81. 

General  Discussion  of  an  Outline  for  the  First  Part  of  an  Intro- 
ductory Course. 

In  the  foregoing  there  has  been  presented  (page  38)  the 
first  fundamental  principle  for  the  selection  of  topics  in  this 
course,  which  principle  may  be  restated  thus:  make  the  course 
primarily  a  presentation  of  experimental  facts  and  introduce 
theory  to  as  slight  an  extent  as  possible. 

The  second  fundamental  principle  governs  the  arrangement 
of  the  material.  This  should  be  arranged  with  the  view  of 
presenting  at  first  only  simple  types  of  reactions,  particularly 
reactions  of  hydration  and  metathesis,  and  deferring  the  pres- 
entation of  the  more  complex  types  until  the  simpler  types 
have  received  thorough  consideration. 

In  the  arrangement  of  subjects  found  in  most  text  books 
neither  the  general  types  of  reactions  nor  any  classification  ac- 
according  to  the  most  prominent  chemical  properties  of  the 
substances  have  been  considered.  Thus,  nitrogen  and  its  com- 
pounds are  invariably  presented  very  early  in  the  course,  al- 
though the  reactions  between  nitric  acid  and  metals  are  always 
complex.  They  involve  not  only  the  simple  reactions  of  hydra- 


48  University  of  Texas  Bulletin 

tion  and  double  decomposition,  but  they  also  involve  oxida- 
tion and  reduction,  and  hence  they  should  really  be  placed  at  a 
point  farther  on  in  the  course.  Again,  many  simple  reactions 
which  are  presented  by  the  interaction  of  salts  of  metals  with 
common  reagents,  such  as  silver  nitrate  with  hydrochloric  acid, 
ferric  chloride  with  sodium  hydroxide,  etc.,  are  usually  given 
at  the  end  of  the  course,  and  yet  they  are  the  simplest  kinds 
of  chemical  changes.  As  a  result  of  the  constant  mixing  up  of 
all  kinds  of  changes  from  the  very  beginning  of  the  course,  the 
student  generally  fails  to  grasp  the  fundamental  principles  in 
any,  and  instead  of  learning  the  properties  of  elements  and  com- 
pounds in  their  proper  relation,  that  is,  each  as  an,  example  of  a 
general  fact,  he  tries  to  learn  them  all  as  isolated  specific  prop- 
erties. 

During  the  last  thirty  years  our  knowledge  of  reactions  in 
aqueous  solutions  has  increased  so  much  that  we  may  now  be 
certain  of  the  fundamental  facts  concerning  them:  it  is  defi- 
nitely known  that  metathetical  reactions  depend  upon  the  de- 
gree of  ionic  dissociation,  while  reactions  involving  oxidation 
and  reduction  depend  upon  additional  facts,  namely,  those 
learned  in  the  study  of  the  galvanic  batteries.  The  study  of 
chemistry  is  immensely  simplified  by  the  application  of  this 
knowledge  and  a  course  arranged  to  set  forth  clearly  these  two 
fundamental  types  of  chemical  changes  will  enable  the  student 
to  get  a  grasp  of  the  chemically  important  properties  of  sub- 
stances which  is  otherwise  not  so  easily  obtained.  For  this 
reason  it  is  advised  here  to  arrange  the  material  according  to 
our  second  fundamental  principle;  more  particularly,  it  is  ad- 
vised to  present  at  first  only  substances  which  undergo  reac- 
tions of  hydration  and  metathesis,  and  then  to  present  later  on 
reactions  involving  changes  of  valence. 

Although  the  arrangement  of  the  subject  matter  according 
to  this  principle  is  quite  different  from  that  found  in  text- 
books, it  will  not  be  found  difficult  to  follow  this  principle  while 
using  any  good  text.  In  order  to  make  it  convenient  for  teach- 
ers to  do  this,  a  detailed  outline  of  the  course  prepared  for  this 
purpose  is  presented  on  pages  62  to  111.  This  outline  is  also 
issued  separately  so  that  it  may  be  put  into  the  bands  of  every 
student.  The  special  experiments  and  directions  which  are 


Chemistry  in  High  Schools  49 

not  found  in  text  books  have  been  written  out  fully.  It  is  in- 
tended that  this  outline  may  be  used  together  with  any  one  of 
the  text-books  and  laboratory  manuals  listed  on  page  60.  The 
separate  prints  of  the  outline  may  be  obtained  from  the  author. 

An  examination  of  this.  Outline  of  the  Course  (see  page  62) 
will  show  that  in  its  first  part  it  differs  only  slightly  from  the 
presentation  usually  given;  but  farther  on  in  the  presentation 
of  the  fundamental  facts  involved  in  metathetical  reactions  it 
differs  radically  from  what  is  ordinarily  found  in  texts.  For 
details,  see  pages  73  to  80. 

Since  the  reactions  of  the  compounds  of  the  metals  involve 
nothing  but  metathetical  reactions,  these  reactions  are  taken 
up  next  in  order  after  the  general  discussion  of  the  metathet- 
ical reaction. 

How  much  of  the  reactions  of  the  compounds  of  the  metals 
should  be  taught  in  such  a  course  as  this?  This  has  been,  and 
possibly  is  still  a  great  question.  On  one  point,  however,  there 
is  unaniminity  of  opinion,  and  that  is :  systematic  qualitative, 
analysis  must  not  be  attempted  in  a  high  school  course. 

But  this  leaves  us  with  the  question:  which  of  the  reactions 
of  the  metals  should  be  taught  and  how  should  they  be  taught  T 
An  examination  of  the  laboratory  manuals  now  on  the  market 
reveals  great  differences  of  opinion.  Some  manuals,  such  as 
Alexander  Smith's  and  B.  W.  Feet's  present  the  reactions  found 
in  the  ordinary  outline  for  qualitative  analysis,  the  only  differ- 
ence between  this  arrangement  and  that  used  in  qualitative 
analysis  being  that  in  this  case  the  reactions  are  presented  dis- 
connectedly, and  outlines  for  the  systematic  analytical  procedure 
are  deliberately  omitted. 

Other  manuals  such  as  the  Laboratory  Exercises  by  Brownlee 
and  Others  make  no  particular  attempt  to  teach  the  reactions  of 
the  metals;  but  the  latter  book  in  Exercises  47  to  51  indicates 
that  it  is  desirable  to  present  certain  features  of  this  work. 
These  features,  which  all  authors  are  trying  to  present  by  their 
various  methods,  may  be  summed  up  as  follows: 

1.  To  change  or  transpose   a  metal   from  one  of  its  com- 
pounds to  another  by  means  of  the  common  reagents. 

2.  To  separate  the  compound  of  a  metal  out  of  its  mixture 
with  compounds  of  other  metals. 


50  University  of  Texas  Bulletin 

3.     To  recognize  or  identify  a  certain  metal  in  its  compounds. 

The  first  object  is  illustrative  of  the  methods  of  manufacture 
of  many  commercially  important  salts  and  compounds  from  the 
commercial  sources  of  the  metal.  The  second  is  particularly 
illustrative  of  the  chemical  purifying  of  substances.  The  object 
of  the  third  is  self-evident.  There  can  be  no  question  as  to  the 
desirability  of  including  some  of  this  work  in  the  course  and  the 
only  thing  we  need  to  consider  is  its  extent  and  the  method  of 
treatment.  With  reference  to  its  extent,  that  presented  by 
Brownlee  and  Others  is  inadequate,  while  that  presented  by 
Smith  and  by  Peet  requires  too  much  time.  Newell  uses  the 
same  method  as  Smith  and  as  Peet,  but  he  attempts  to  save  time 
by  lessening  the  number  of  exercises.  This  makes  the  work 
weak,  if  not  utterly  valueless.  As  a  way  out  of  these  various 
difficulties,  the  following  experimental  procedure  is  suggested : 
take  solutions  of  water  soluble  salts  of  the  common  metals 
an.d  study  their  reactions  with  several  general  reagents.  Then 
add  special  properties  of  some  of  the  compounds  of  the  metals 
such  as  the  solubility  of  lead  chloride  in  hot  water,  the  hydrolysis 
of  bismuth  salts,  the  flame  colorations,  etc.  Finally,  add  a  list 
of  exercises  designed  to  make  the  student  use  these  facts  in  the 
solution  of  special  problems.  The  list  of  exercises  given  in 
the  Outline  is  drawn  up  with  this  in  view.  These  reactions  of 
the  metals  give  the  student  enough  experience  with  the  meta- 
thetical  reaction  to  become  well  grounded  in  its  fundamental 
facts.: 

Reactions  involving  oxidation  and  reduction — i.  e.,  involving 
changes  in  valence — may  be  taken  up  next.  These  should  be 
considered  separately  from  hydration  and  metathetical  changes 
because  they  involve  entirely  different  fundamental  facts.  They 
'should  not  be  considered  until  after  changes  of  hydration  and 
metathetical  reactions  have  been  fully  mastered,  because  they  in- 
volve the  latter. 

The  terms  oxidation  and  reduction  are  rather  misleading; 
many  changes  to  be  considered  under  this  heading  do  not  involve 
oxygen  in  any  apparent  manner.  As  the  terms  are  now  used, 
their  direct  significance  is  as  follows :  oxidation  is  an  increase 
of  positive  electric  charges  on  an  element  or  radical  (or  the  ab- 


Chemistry  in  High  Schools  51 

straction  of  negative  electric  charges)  ;  and  reduction  is  the  re- 
verse electric  change.  The  conception  involved  here  can  not  be 
considered  without  a  study  of  the  action  of  battery  cells,  because 
the  battery  cell  is,  in  a  sense,  an  experimental  analysis  of  oxida- 
tion and  reduction  reactions  which  presents  the  essential  parts  in 
their  true  relation.  Any  mixture  in  which  oxidation  and  re- 
duction take  place  represents  merely  the  case  in  which 
the  electric  charges,  instead  of  being  transferred  by  means  of 
conducting  poles  and  their  connecting  wires,  are  transferred  by 
direct  contact  between  the  two  parts  undergoing  the  changes  in 
valence.  Hence  battery  cells  should  be  studied  in  this  connection 
(see  pages  87  to  91). 

Following  this  presentation  of  the  battery  cell,  oxidation  and 
reduction  may  be  introduced  as  given  on  pages  101  to  111. 

The  question  now  arises :  How  much  of  this  last  subject  should 
be  taught  in  a  high  school  course?  The  greatest  danger  is  to 
attempt  too  much  of  it.  The  work  presented  in  the  accompany- 
ing outline,  extending  through  the  oxidizing  actions  of  nitric 
acid  (to  page  108)  is  as  much  as  should  ~be  given.  However 
after  this,  whenever  in  the  presentation  of  descriptive  matter 
connected  with  any  topic  there  occur  equations  for  oxidation  and 
reduction  actions,  then  the  valences  of  the  ''valence-changing 
elements ' '  or  radicals  should  be  plainly  marked  in  the  equations, 
as  shown  in  the  accompanying  introduction  to  this  subject  (see 
page  106).  By  this  means  the  equations  will  be  made  vastly 
more  significant  than  without  it. 

Other  Subjects  That  May  Be  Studied. 

Beyond  this  point  other  subjects  may  be  taken  up  in  almost 
any  order  that  may  appear  desirable. 

The  following  subjects  are  worthy  of  consideration  here: 
(a)  elements  not  yet  studied  and  their  important  compounds, 
fb)  theoretical  topics,  such  :as  the  atomic  and  molecular  the- 
ories, 

(c)  topics  of  practical  interest. 

Under  (a)  the  following  subjects  may  be  considered:  first 
of  all,  the  halogens  (bromine,  iodine,  fluorine),  if  they  have  not 


52  University  of  Texas  Bulletin 

been  previously  studied;  then  any  of  the  following  in  whatever 
order  desired :  phosphorus,  arsenic,  boron,  manganese,  chromium, 
and  the  oxy-halogen  compounds.  Only  a  few  of  the  most  com- 
mon experimental  facts  should  be  considered.  The  classification 
of  the  elements  according  to  the  periodic  system  should  be 
pointed  out  briefly. 

Under  (b)  in  connection  with  the  atomic  theory,  the  law  of 
definite  proportion  and  the  law  of  simple  multiple  proportion 
may  be  considered.  The  law  of  combining  weights  (see  Smith's 
College  Chemistry,  page  34)  is  probably  too  difficult  and  may 
just  as  well  be  omitted.  At  this  period  of  the  student 's  develop- 
ment, it  would  not  be  out  of  place  to  present  the  philosophical 
considerations,  which,  based  upon  these  general  facts,  have  built 
up  the  conception  of  the  atomic  structure  of  matter.  However, 
do  not  mix  with  this  topic  any  consideration  of  the  molecular 
theory  based  on  Avogodro's  Hypothesis.  This  mistake  is  found 
in  many  texts,  and  must  be  guarded  against  It  is  very  de- 
sirable to  give  some  quantitative  experiments  in  connection  with 
this  topic,  such  as  the  determination  of  the  hydrogen  equiv- 
alents of  metals,  or  the  ratio  in  which  metals  combine  with 
oxygen  or  with  chlorine.  In  the  choice  of  these  experiments 
the  teacher  must  exercise  great  care  to  select  those  only  that  arc 
most  easily  and  accurately  carried  out.  The  law  of  definite  pro- 
portion may  also  be  illustrated  by  the  repeated  titration  of  a 
base  with  an  acid,  using  different  quantities  each  time.  Other 
suitable  quantitative  experiments  are  determinations  of  the  sol- 
ubilities of  salts,  the  determination  of  water  of  crystalliza- 
tion in  salts,  etc.  Good  workable  quantitative  experiments  are 
found  in  Smith,  Chap.  7. 

If  the  molecular  theory,  and  Avogodro's  Hypothesis  are  in- 
troduced, several  fundamental  demonstrations  should  be  made. 
If  such  demonstrations  cannot  be  made,  then  it  is  questionable 
whether  the  topic  should  be  taken  up  at  all.  The  following 
three  experiments  are  probably  the  simplest  and  most  work- 
able that  can  be  used  in  this  connection,  and  those  wishing  to 
present  this  topic  are  strongly  advised  to  perform  these,  at 


Chemistry  in  High  Schools  53 

Experiments  Which  Should  Accompany  the  Study  of  Avogat- 
dro's  Hypothesis. 

(1) .  To  DETERMINE  THE  KATIO  BY  VOLUME  IN  WHICH  HYDRO- 
GEN AND  OXYGEN  COMBINE  TO  FORM  WATER. 

For  this  purpose  it  is  advisable  to  secure  a  specially  made 
eudiometer  tube  constructed  as  follows:  a  very  heavy  glass 
tube  of  50-60  cm.  length  and  about  100  cc.  capacity  terminates 
in  both  ends  in  stout  tubes  with  a  small,  almost  capillary,  bore, 
in  which  are  fitted  specially  well  ground  stop-cocks.  One  of  these 
terminal  tubes  should  be  bent  twice  at  a  right  angle,  its  stop- 
cock should  be  placed  about  1  inch  from  the  open  end  of  the  cap- 
illary tube,  and  the  tube  should  be  calibrated,  beginning  at  the 
stop-cock  and  marking  every  half  cc.  The  tube  should  also  be  sup- 
plied with  platinum  wire  electrodes  placed  in  the  wide  tube  near 
the  end  to  which  the  bent  capillary  terminal  is  attached.  It  should 
be  specified  that  the  connecting  loops  of  the  platinum  wire  elec- 
trodes outside  of  the  tube  should  be  constructed  so  as  not  to 
be  easily  breakable.  In  addition  to  this  tube  there  should  be  se- 
cured a  Hoffmann  electrolytic  apparatus  such  as  is  shown  in 
Eimer  &  Amend 's  catalog  No.  3902.  It  should  be  specified, 
however,  that  the  terminal  tubes  in  which  the  stop-cocks  are 
placed  and  through  which  the  gases  may  be  discharged,  should 
have  a  small,  almost  capillary  bore,  and  it  should  also  be  specified 
that  the  outer  terminals  of  the  electrodes  should  be  specially 
well  constructed  so  as  to  be  practically  unbreakable.  To  fill  the 
eudiometer  with  hydrogen  and  oxygen  it  is  first  filled  with  water 
by  suction,  care  being  taken  to  fill  the  connecting  tubes  with 
liquid.  The  eudiometer  is  then  placed  beside  the  elec- 
trolytic apparatus,  the  bent  end  of  the  eudiometer  tube 
is  connected  by  means  of  a  piece  of  rubber  tubing 
with  one  of  the  gas-discharging  tubes  of  the  electrolytic 
apparatus,  care  being  taken  to  bring  the  two  ends  of  the  glass 
tubes  in  direct  contact.  About  20  cc.  of  hydrogen  and  exactly 
half  as  much  oxygen  are  thus  transferred  to  the  eudiometer. 
In  measuring  the  gases  in  the  eudiometer  the  differences  in 
pressure  due  to  the  differences  in  the  heights  of  the  column  of 
water  in  the  eudiometer  tubes  may  be  neglected.  The  total  vol- 


54  University  of  Texas  Bulletin 

ume  of  explosive  mixture  used  should  not  exceed  25  cc.  or  at 
most  30  cc.,  since  otherwise  the  explosion  may  shatter  the  tube. 
Before  exploding  the  mixture  the  lower  stop-cock  is  also  closed. 
The  lower  end  of  the  tube  should  extend  into  some  water  in  a 
beaker,  and  after  the  explosion  the  lower  stop-cock  should  be 
opened  rather  cautiously,  so  that  the  inrush  of  the  water  may 
not  shatter  the  tube. 

This  apparatus  is  simple,  and  easy  to  handle,  and  by  its  means 
it  is  easy  to  demonstrate  exactly  that  two  volumes  of  hydrogen 
combine  with  one  volume  of  oxygen.  Even  at  the  risk  of  being 
tedious  the  author  cannot  refrain  from  pointing  out  again  that 
this  fact  cannot  be  demonstrated  by  means  of  the  simple  elec- 
trolysis of  dilute  sulphuric  acid, — which  is  erroneously  desig- 
nated as  the  electrolysis  of  water.  In  this  case,  the  production 
of  the  two  gases  is  due  to  two  entirely  separate  reactions,  as 
has  been  pointed  out  elsewhere.  Frequently  the  ratio  of  the 
volume  of  the  hydrogen  to  the  volume  of  the  oxygen  obtained 
by  electrolysis  is  even  greater  than  "two,"  on  account  of  the 
fact  that  not  all  of  the  reaction  at  the  anode  produces  simple 
oxygen  gas. 

Since,  for  the  same  reason  the  electrolysis  of  hydrochloric 
acid  cannot  be  considered  to  be  a  demonstration  of  the  fact  that 
one  volume  of  hydrogen  combines  with  one  volume  of  chlorine 
to  form  hydrochloric  acid,  it  appears  to  be  desirable  to  demon- 
'strate  the  direct  union  of  hydrogen  and  chlorine.  However, 
this  reaction  is  so  violent  and  so  troublesome  that  it  is  not  ad- 
visable to  attempt  it  for  classroom  demonstration.  Mere  men- 
tion of  the  experimental  result  should  be  made  in  this  connec- 
tion. 

(2)     To  DEMONSTRATE  THE  RATIO  BY  VOLUME  BETWEEN  Aw- 

MONIA  GAS  AND  THE  NlTROGEN  OBTAINED  FROM  IT. 

The  next  important  point  to  demonstrate  is  to  show  the  volume 
relation  between  original  and  resulting  gases.  For  theoretical 
reasons  it  would  be  most  advisable  to  use  the  example  just  re- 
ferred to,  by  means  of  which  it  would  be  found  that  half  a 
tube  of  hydrogen  plus  half  a  tube  of  chlorine  would  give  a  tube 


Chemistry  in  High  Schools  55 

full  of  hydrochloric  acid  gas.  On  account  of  the  difficulty  of 
performing  this  experiment  it  is  inadvisable  to  use  it  as  a  dem- 
onstration. To  demonstrate  such  a  relation  the  following  ex- 
periment should  be  performed.  A  tube  full  of  dry  ammonia  gas 
should  be  treated  with  bromine  (more  specifically  sodium  hypo- 
bromite)  by  means  of  which  all  the  hydrogen  in  the  ammonia 
is  abstracted  and  the  nitrogen  left  free.  This  nitrogen,  it  will 
be  found,  occupies  just  one-half  the  volume  occupied  by  the 
ammonia  from  which  it  was  obtained.  The  Hoffman  lecture 
apparatus  tube  for  the  demonstration  of  the  volume  relations 
in  ammonia,  which  tube  is  shown  in  Eimer  &  Amend 's  catalog 
No  3904, — this  tube  should  be  obtained  with  an  additional  stop- 
cock attached  to  the  closed  end.  The  bore  of  the  tube  of  this 
stop-cock  should  not  be  less  than  2  or  3  mm.  and  the  tube  should 
be  cleaned  and  dried  by  rinsing  it  first  with  water  and  after- 
wards with  alcohol,  and  finally  drawing  air  through  it  with  the 
aid  of  the  suction  pump  or  by  means  of  the  foot  pump,  and  at 
the  same  time  warming  the  tube  gently  with  the  flame.  It  is 
clamped  in  a  vertical  position  and  filled  with  ammonia  gas  gen- 
erated by  boiling  a  concentrated  solution  of  ammonia,  and 
passing  it  through  a  drying  tower  filled  with  quicklime.  The  gas 
should  be  passed  in  at  the  top  of  the  tube  at  a  fairly  good  rate. 
After  the  tube  has  been  filled  with  ammonia  and  closed,  it  can 
be  laid  aside  until  the  time  for  the  lecture.  For  the  decomposi- 
tion of  the  ammonia  about  50  to  100  cc.  of  20  per  cent  sodium 
hydroxide  solution  is  treated  with  bromine  until  tfce  solution 
has  a  straw  yellow  color.  The  mixture  must  be  stirred  vigor- 
ously while  adding  the  bromine.  This  solution  is  added  cau- 
tiously through  the  " funnel  end,"  care  being  taken  not  to 
admit  air.  Finally  the  upper  stop-cock  is  closed,  and  the  lower 
stop-cock  is  opened  while  this  end  of  the  tube  is  dipped  under 
water  so  that  the  latter  may  rise  in  the  tube  until  the  pressure 
inside  the  tube  is  equal  to  the  atmospheric  pressure. 

This  experiment  is  very  easily  performed,  and  gives  the 
facts  for  the  following  argument.  If  the  "tubeful"  of  gas 
contains  "a"  molecules,  then  the  half  "tubeful"  contains 
''a/2"  molecules  and  since  each  one  of  the  "a"  molecules  of 
ammonia  contains  ai  least  one  atoms  of  nitrogen,  then  there 


56  University  of  Texas  Bulletin 

must  be  at  least  "a"  atoms  of  nitrogen  in  "a/2"  molecules  of 
nitrogen,  or  at  least  two  atoms  in  each  molecule  of  nitrogen. 
The  corresponding  facts  concerning  hydrogen  and  chlorine  pro- 
ducing hydrochloric  acid  gas  and  also  hydrogen  and  oxygen 
producing  steam,  with  the  same  argument,  lead  to  the  conclu- 
sion that  the  molecules  of  hydrogen,  of  chlorine,  and  of  oxygen, 
each  contain  at  least  two  atoms. 

(3)  To  DEMONSTRATE  THE  RATIO  BY  VOLUME  BETWEEN  OXY- 
GEN AND  THE  SULPHUR  DIOXIDE  FORMED  FROM  IT. 

For  this  purpose  secure  a  piece  of  hard  glass  tubing  about  24 
inches  long,  closed  at  one  end,  and  bent  almost  at  right  angle 
at  a  point  about  5  inches  from  the  closed  end.  Place  a  little 
sulphur  in  the  closed  end  of  the  tube  and  fasten  it  there  by 
melting  the  sulphur  slightly.  Then  fill  the  tube  partly  with 
oxygen  over  mercury  and  place  it  with  the  short  arm  in  a  hori- 
zontal position.  The  action  is  started  by  gently  heating  the 
sulphur.  Usually  no  gas  will  escape,  and  after  the  tube  has 
been  allowed  to  cool,  the  mercury  will  rise  to  the  original  posi- 
tion, which  shows  that  the  volume  of  the  sulphur  dioxide  is 
equal  to  the  volume  of  the  original  oxygen. 

Chemical  Information  of  Direct  Economic  Value  in  Texas. 

Perhaps  the  most  important  additional  topic  to  be  added  to 
the  course  is  the  presentation  of  subjects  of  practical  interest. 
While  the  two  preceding  topics  may  be  omitted  entirely  with- 
out any  loss  to  the  student,  this  last  topic  should  not  be  omitted, 
because  the  major  part  of  the  direct  value  of  the  course  to  the 
high  school  student  is  obtained  through  the  proper  conveyance 
of  accurate  information  on  practical  subjects  with  which  he 
will  have  to  deal  more  or  less  during  the  rest  of  his  life.  The 
value  of  such  work  and  the  desirability  of  presenting  it  in  this 
course  have  never  been  doubted,  but  the  results,  obtained  by 
many  of  the  attempts  made  to  present  it,  have  frequently  been 
worth  very  little,  and  occasionally  they  even  serve  to  discredit 
both  subject  and  teacher  in  the  eyes  of  the  general  public.  This 
back  set,  in  general,  is  due  to  two  causes :  the  first  is  the  ignorance 


Chemistry  in  High  Schools  57 

of  many  teachers  in  the  practical  application  of  chemistry, 
and  the  second  is  a  mistaken  method  of  presenting  it  due  to 
the  zeal  of  the  teacher  to  give  this  subject  prominence.  The 
subject  is  so  important  that  proper  methods  of  presentation 
and  errors  to  be  avoided  should  be  given  here. 

Teachers  just  beginning  to  teach  chemistry,  whether  college 
graduates  or  trained  in  other  ways,  are  as  a  rule,  not  only 
ignorant  of  the  practical  applications  of  the  subject,  but  their 
interest  in  the  pure  science,  inclines  them  to  stress  the  pure, 
scientific  subjects  to  the  exclusion  of  the  practical  ones.  If 
they  continue  to  teach  the  subject,  sooner  or  later  they  are 
impressed  with  the  importance  of  the  practical  applications 
and  in  their  effort  to  give  this  prominence,  they  may  go  to  the 
other  extreme.  The  writer  has  at  hand  some  outlines  prepared 
by  prominent  teachers  of  chemistry  in  various  parts  of  the 
United  States,  in  which  an  attempt  is  made  to  introduce  prac- 
tical subjects  from  the  very  beginning  of  the  course.  Long 
before  the  student  has  any  knowledge  of  the  simple  chemical 
facts  involved,  these  outlines  present  problems  of  water  soften- 
ing, the  testing  of  coal  gas  for  impurities,  the  solvent  action  of 
water  on  lead,  the  tests  for  organic  matter  in  potable  water, 
etc.  Such  information,  though  valuable  in  itself,  becomes 
valueless  when  presented  so  early  in  the  course  that  the  stu- 
dent's lack  of  knowledge  of  pure  chemical  phenomena  pre- 
vents a  recognition  of  the  simple  fundamental  phenomena  in- 
volved. The  mere  mechanical  testing  of  certain  constituents 
of  a  potable  water  before  the  student  has  even  learned  or  seen 
reactions  between  pure  salt  solutions,  such  as  the  reaction  be- 
tween sodium  carbonate  and  calcium  chloride,  cannot  be  of 
much  value  either  as  an  informational  or  as  a  training  exer- 
cise. 

Another  mistake  is  the  selection  of  applications  which  are 
nothing  but  empiric  operations.  Thus  we  find  various  at- 
tempts made  to  present  the  chemistry  of  cooking,  the  chemistry 
of  cleaning,  etc.,  under  which  headings  many  useful  topics  are 
offered.  When,  however,  such  subjects  are  presented  by  them- 
selves, and  particularly  when  the  presentation  crowds  out  fun- 
damental chemical  phenomena,  they  degrade  the  course  into 
the  mere  "trying  out"  of  a  number  of  shop  recipes. 


58  University  of  T&xas  Bulletin 

A  course  filled  with  such  material  cannot  give  a  well  devel- 
oped exposition,  of  the  subject.  However,  the  entire  neglect 
of  these  (applications  is  probably  just  as  great  a  mistake.  The 
problem  to  be  solved  is  to  present  enough  of  the  fundamentals 
to  give  the  student  some  sound  training  and  then  to  add  suffi- 
cient applications  to  give  the  subject  "life."  The  first  thing 
necessary  to  accomplish  this  end  is  for  the  teacher  to  read  and 
study  in  order  to  inform  himself  on  practical  subjects.  As  a 
rule  he  will  not  get  this  information  in  college:  he  must  se- 
cure it  by  informing  himself  in  a  general  way, — as  for  in- 
stance, by  reading  books  affording  information  on  practical 
topics,  by  noting  the  operations  and  practices  of  practical  men 
and  artisans  around  him,  etc.  To  be  more  definite,  he  should 
attempt  to  inform  himself  on  such  subjects  as  the  following: 
soils,  fertilizers,  and  irrigation  waters;  feed  and  food-stuffs; 
the  technology  of  petroleum  oils,  tar  oils,  cotton  seed  oil,  lin- 
seed oil,  the  manufacture  of  soap,  paints,  paper,  etc.  The  fol- 
lowing books  will  furnish  him  with  a  great  deal  of  information 
on  these  subjects: 

Soils  and  Fertilizers,  by  Harry  Snyder  (The  Macmillan  Co.). 

Alkali  Soils  and  Irrigation  Waters,  by  G.  S.  Fraps,  Bull. 
130  of  the  Texas  Agricultural  Exp.  Station. 

Nature  and  Use  of  Commercial  Fertilizers,  G-.  S.  Fraps,  Bull. 
112,  Texas  Agricultural  Exp.  Station. 

Outlines  of  Industrial  Chemistry,  by  F.  H.  Thorp  (The 
MacMillan  Co.). 

Chemistry  of  Plant  and  Animal  Life,  Harry  Snyder  (The 
MacMillan  Co.). 

In  the  study  of  these  subjects  it  will  be  found  advisable  to 
direct  the  attention  to  the  following  points : 

The  chemical  analysis  of  a  soil  at  present  does  not  enable 
one  to  judge  what  ails  an  infertile  soil;  the  value  of  fertil- 
izers is  determined  by  "pot"  or  "basket"  experiments;  the 
essential  constitutents  of  fertilizers  are  the  nitrogen,  potas- 
sium /and  phosphorus  compounds  in  it;  why  rotation  of  crops 
is  necessary;  the  Texas  feed  analysis  law  requires  the  deter- 
mination of  carbohydrates,  fats,  proteins,  indigestible  matter 
or  crude  fiber,  water  and  mineral  solids ;  what  is  meant  by  these 
divisions  of  food  stuffs  and  how  they  are  experimentally  deter- 


Chemistry  in  High  Schools  59 

mined;  the  relative  proportions  of  these  constituents,  in  food 
or  feedstuffs;  the  essential  properties  of  the  three  classes  of 
foodstuffs,  that  is,  of  carbohydrates,  of  fats,  and  of  proteins; 
starch  can  be  converted  to  dextrine  and  to  glucose,  and  the 
latter  can  be  fermented  to  alcohol;  fats  of  vegetable  or  animal 
origin  can  be  used  to  make  soap;  how  cotton  seed  oil  is  made 
and  refined;  the  essential  difference  between  cotton  seed  oil 
and  linseed  oil,  which  makes  the  latter  valuable  to  be  used  in 
paints;  white  lead  is  the  most  valuable  pigment  for  paints  and 
the  best  paints  contain  this  together  with  just  enough  of  some 
coloring  matter  to  give  the  desired  tints;  the  essential  constitu- 
ents of  coal  and  their  determination;  how  hard  waters  may  be 
softened  cheaply  for  boiler  purposes ;  how  potable  waters  may  be 
purified  in  case  they  are  unsanitary ;  how  kerosene,  gasoline,  par- 
affin, etc.,  are  obtained  from  crude  petroleum  and  how  they  may 
be  refined;  what  is  meant  by  the  flash  point  of  kerosene;  oils 
obtained  by  the  distillation  of  tar  are  chemically  more  active 
than  petroleum  oils  and  hence  form  the  starting  point  of  the 
many  synthetic  dyes  iand  drugs ;  oils  obtained  from  tar,  in  con- 
tradistinction to  the  oils  obtained  from  petroleum,  are  germi- 
cidal,  and  hence  the  cheapest  portions  of  the  tar  distillates  are 
used  for  wood  preservation;  how  cement  is  made;  the  chemis- 
try of  photography  and  of  blue-printing,  etc. 

If  the  teacher  has  no  knowledge  of  organic  chemistry,  he 
should  study  certain  parts  of  Remsen's  Organic  Chemistry. 
This  book,  though  small,  will  give  him  the  necessary  scientific 
foundation  for  the  parts  in  the  foregoing  list  which  deal  with 
organic  chemistry. 

The  introduction  of  this  information  into  the  course  is  rather 
difficult  at  present  on  account  of  the  absence  of  a  suitable  text- 
book. The  best  text-books  on  the  market  today  present  a  good 
introduction  to  the  science,  but  do  not  present  in  any  adequate 
manner  such  "practical"  information  as  above  indicated. 

It  is  difficult  to  say  how  much  of  this  can  be  done  in  a  high 
school  course,  but  it  is  certain  that  none  will  be  done  unless 
the  teacher  is  actively  engaged  in  increasing  his  own  knowledge 
in  this  line.  Young  teachers  in  chemistry  frequently  continue 
their  collegiate  course  by  attending  summer  schools,  and  in  this 
way  they  increase  their  knowledge  of  pure  chemistry.  Such 


60  University  of  Texas  Bulletin 

a  practice  is  extremely  commendable  <and  valuable  for  both  the 
teacher  and  his  school,  but  unless  he  makes  a  special  effort 
outside  of  the  college  course  to  increase  his  knowledge  of  chem- 
ical applications,  his  knowledge  of  the  subject  and  hence  his 
teaching  will  continue  to  be  one-sided  and  much  less  fruitful  than 
if  he  also  increases  his  knowledge  of  practical  affairs. 

The  University  of  Texas  Requirements  for  One  Unit  Entrance 

Credit. 

The  suggestions  and  directions  in  this  paper  need  not  be 
followed  to  secure  affiliation  in  chemistry  at  the  University 
of  Texas.  They  are  offered  to  teachers  as  aids  in  shaping  their 
courses  in  chemistry,  and  whether  or  not  these  suggestions  are 
followed  has  nothing  to  do  with  securing  (affiliation.  The  Uni- 
versity aims  to  be  exceedingly  liberal  and  broad-minded  in  its 
requirements  for  affiliation  as  shown  by  the  following  list  of 
requirements. 

1.  A  properly  prepared  teacher : — see  page  9. 

2.  A  proper  class-time  allowance.     The  time  spent  in    the 
course  must  not  be  less  than  three  recitation  periods  of    45 
minutes  and  two  90  minute  laboratory  periods  a  week  for  one 
year. 

3.  A  fairly  well  equipped  laboratory  in  which  the  students 
do  individual  work. 

4.  Some  evidence  that  the  (competent)  teacher  occupies  the 
time  with   a  well  planned  and  well   conducted  course.     This 
evidence  is  obtained  by  a  personal  visit  of  an  official,  and  an 
inspection  of  the  note  books  and  examination  papers  of    the 
students  in  the  course. 

Some  Suitable  Text  Books  in  Chemistry. 

Brownlee  &  Others,  First  Principles  of  Chemistry,  Allyn  & 
Bacon. 

Hollis  Godfrey,  Elementary  Chemistry,  Longmans,  Green  & 
Co. 

Hessler  and  Smith,  Essentials  of  Chemistry,  Benjamin  San- 
born  Co. 


Chemistry  in  High  Schools  61 

McPherson  and  Henderson,  Elementary  Chemistry,  Ginn  & 
Co. 

Morgan  &  Lyman,  Elementary  Text  on  Chemistry,  MacMil- 
lan  Co. 

Newell,  Inorganic  Chemistry,  D.  C.  vHeath  &  Co. 

B.  W.  Peet,  Laboratory  Manual  in  Chemistry,  published 
by  the  author  at  Ypsilanti,  Mich. 

Remsen,  Introduction  to  Chemistry  (Briefer  Course)1.,  H. 
Holt  &  Co. 

Smith,  Laboratory  Outline  of  General  Chemistry  (4th  Edi- 
tion) Century  Co.  This  is  the  book  referred  to  in 
Part  III  where  Smith  appears.  It  is  primarily  a 
college  text,  but  is  likely  to  be  in  the  hands  of  every 
teacher,  and  the  author  preferred  to  refer  to  it  alone 
rather  than  to  all  the  high  school  texts. 

Smith  &  Hall,  The  Teaching  of  Chemistry  and  Physics  in 
Secondary  Schools,  Longmans,  Green  &  Co. 

Alexander  Smith,  Inorganic  Chemistry,  Century  Co. 

Julius  Stieglitz,  Qualitative  Analysis,  Century  Co. 

Prescott  &  Johnson,  Qualitative  Analysis,  Van  Nostrand  Co. 

Roscoe  &  Schorlemmer,  Inorganic  Chemistry,  2  volumes, 
MacMillan  Co. 


PART  III.* 

OUTLINE  OF  AN  INTRODUCTION  TO  THE  FIRST  PRIN- 
CIPLES OF  CHEMISTRY,  t 

Oxygen. 

1.  Demonstration  of  its  preparation  by  the  decomposition 
of  oxygen  compounds  at  high  temperatures  (Smith,  Art.  10). 
The  weight  relations  of  the  substances  which  decompose  giving 
oxygen  are  as  follows: 

Ba02=BaO+0 

Pb02=--PbO+0 


3Mn02=Mn304+20 
KC103=HC1+30 

The  names  of  these  substances  and  the  above  information  con- 
cerning the  quantities  involved  in  the  reactions  should  be  com- 
mitted to  memory  by  the  students.  "These  are  particular  sub- 
stances which  show  the  general  behavior  of  giving  up  oxygen 
readily  at  high  temperatures."  Note  the  significance  of  co- 
efficients and  subscripts  in  chemical  formulae  and  equations. 
Fundamentally  the  symbols  represent  a  certain  number  of  parts 
by  weight  of  a  particular  substance,  which  number  is  given  in 
an  accompanying  table  commonly  referred  to  as  a  table  of 
atomic  weights.  The  student  should  not  stumble  at  the  word 
"atomic  weights,"  —  he  should  simply  accept  this  for  the  pres- 
ent as  merely  a  name  for  the  table.  The  quantitative  signifi- 
cance of  the  symbols  and  equations  should  be  emphasized  by 
problems  based  on  them. 

2.  Catalytic  Effect  of  Manganese  Dioxide  in  the  Decomposi- 
tion of  Potassium  Chlorate  (Smith,  Art.  11). 

Avoid  presenting  Mn02  in  the  equation  for  the  decomposi- 
tion of  potassium  chlorate;  equations  are  expressions  of  quan- 
titative relations  only,  and  the  manganese  dioxide  undergoes  no 

*This  part  has  been  issued  separately  by  the  author. 
•{•Copyrighted,  1912,  by  E.  P.  Schoch. 


Chemistry  in  High  Schools  63 

change  and  is  not  necessarily  present  in  any  particular  propor- 
tion, hence  its  quantity  is  not  involved  and  should  not  appear 
in  the  equation. 

3.  Preparation  and  Collection  of  Several  Bottles  Full  of  the 
Gas,  and  the  Combustion  of  Sulphur,  Phosphorus,  Carbon,  So- 
dium and  Iron  In  It.  Perform  this  in  the  usual  manner.  This 
shows  experimentally  that  oxygen  is  very  slightly  soluble  in 
water,  that  it  is  a  colorless  inodorous  gas,  that  it  is  as  heavy  as — if 
not  heavier  than — air,  etc.  Students  should  learn  these  proper- 
ties from  experiments  rather  than  from  the  printed  page. 

The  products  of  combustion  should  be  treated  with  water  and 
the  resulting  solutions  tested  with  litmus.    These  substances  react 
with  water  in  the  following  proportions: 
C02+H20=H2CO, 
S02+H20=H2S03 
P205+3H20=2H3P04 
Na20+H20=2NaOH 
Fe203  does  not  react  with  water. 

These  equations  are  to  be  memorized  and  their  quantitative 
significance  to  be  emphasized  with  numerical  problems.  Such 
reactions  with  water  are  called  hydration  and  this  is  a  very 
common  chemical  phenomenon.  Note  the  general  fact  here  illus- 
trated, that  non-metals  form  acid  oxides  and  metals  form  basic 
oxides.  This  is  a  fundamental  fact  and  should  be  remembered. 

Hydrogen. 

1.  General  facts  concerning  its  preparation:  the  interaction 
of  metals  and  acids: 

(a)  Many  non-oxidizing  acids  (hydrochloric,  dilute  sulphu- 
ric, acetic,  phosphoric)  react  with  any  metal  above  hydrogen  in 
the  electromotive  force  table  (e.  g.  iron,  zinc,  aluminium,  mag- 
nesium— see  page  110)  to  form  hydrogen  and  one  other  prod- 
uct (salt)  ;  while  there  is  no  action  with  the  metals  below  hydro- 
gen in  the  table. 

(b)  Oxidizing    acids     (nitric    acid,   concentrated  sulphuric 
acid)   act  on  almost  all  metals  except  the  lowest  in  the  table 
(gold,  platinum) ;  but  hydrogen  does  not  appear  as  one  of  the 
products,  and  the  action  is  altogether  more  complex  than  any 
action  with  non-oxidizing  acids. 


64  University  of  Texas  Bulletin 

The  above  general  facts  (a  and  b)  should  be  learned  and  re- 
tained by  the  student.  He  should  realize  that  by  this  means  he 
learns  a  great  number  of  important  facts  easily. 

In  connection  with  (a)  the  following  quantitative  data  is 
given: 

Fe-f2HCl=FeCl2+2H 
Zn+2HCl= ZnCl2+2H 
A1+3HC1=A1C13+3H 
Fe+H2SO4=FeS04+2H 
Zn+H2SO4= ZnS04+2H 
2A1+3H2S04=A12  ( S04)  3+6H. 

These  equations  should  be  committed  to  memory  and  drilled 
on  by  means  of  numerical  problems. 

2.  Preparation  and  collection  of  the  gas  to  show  some  of  its 
common  properties.    Perform  as  given  in  any  text.    The  experi- 
ment shows  that  the  gas  is  not  very  soluble  in  water,  that  it  is 
lighter  than  air,  that  it  forms  water  on  burning  and  that  when 
mixed  with  air  in  certain  proportions  it  forms  explosive  mix- 
tures. 

3.  Qualitative  reduction  of  some  metal  oxide  (lead  oxide  or 
copper  oxide),  Smith,  Art.  20.    Point  out  how  this  experimental 
procedure  may  be  used  (as  it  was  used,  by  Dumas)  to  get  the 
proportion  by  weight  in  which  hydrogen  and  oxygen  combine  to 
form  water. 

Incidentally  the  relative  rate  of  diffusion  of  gases  may  be 
demonstrated,  as  usual,  by  means  of  hydrogen  and  air. 

The  change  of  gas  volumes  through  change  of  temperature  and 
pressure  may  also  be  considered  here. 

Chlorine. 

1.  The  reactions  involved  in  the  preparation  of  chlorine  are 
all  complex  reactions  of  oxidation  and  reduction,  hence  the  prep- 
aration of  chlorine  does  not  fit  into  our  general  plan  at  this 
point.  However,  it  is  desirable  to  demonstrate  here  the  proper- 
ties of  the  element.  For  the  reason  just  given,  the  details  of  the 
reactions  involved  in  the  preparation  of  chlorine  are  not  consid- 
ered and  the  general  fact  alone  is  given,  namely,  that  it  is  pre- 
pared by  the  action  of  oxidizing  agents  upon  hydrochloric  acid. 


Chemistry  in  High  Schools  65 

The  oxidizing  agents  serve  in  a  sense  as  suppliers  of  oxygen 
merely,  and  the  oxygen  that  they  supply  combines  with  the  hydro- 
gen of  the  hydrochloric  acid  to  form  water.  The  following  equa- 
tion represents  this  change  and  is  the  only  one  that  should  be 
given  and  learned  in  this  connection : 

0+2HC1=H20+2C1. 

Use  several  oxidizing  agents  to  illustrate  this  general  method 
of  producing  chlorine  (Smith,  Art.  29a). 

2.  Prepare  and  collect  several  bottles  full  of  the  gas  to  dem- 
onstrate some  of  its  properties.  Proceed  as  given  in  any  text. 

Hydrogen  Chloride. 

1.  A  general  method  for  producing  this  substance  is  the  re- 
action between  a  metal  chloride  and  a  relatively  non-volatile  and 
non-oxidizing  (toward  HC1)  acid.  The  mixture  must  not  con- 
tain water  since  otherwise  the  gas  dissolves  in  it.  See  Smith, 
Art.  31  (a)  and  (b).  Call  attention  to  the  fact  that  concentrated 
sulphuric  acid  is  not  an  oxidizing  agent  toward  HC1  while  it  is 
towards  metals. 

The  study  of  water  as  a  solvent,  as  water  of  crytallization, 
etc..  and  of  air,  .its  composition,  etc.,  may  be  introduced  any- 
where here  at  the  option  of  the  instructor. 

Acides,  Bases  and  Salts. 

A  thorough  treatment  of  this  topic  is  advisable  at  this  point. 
The  fundamental  relation  is  "an  acid  with  a  base  gives  a  salt 
and  water."  This  is  the  only  real  criterion  for  the  definition 
of  the  terms  acid,  base  and  salt.  Such  properties  as  the  effect 
upon  litmus  paper,  taste,  etc.,  characterize  only  those  par- 
ticular acids  or  bases  which  are  soluble  and  they  are  not  general 
or  defining  characteristics.  In  order  that  the  above  relation,  that 
an  acid  with  base  gives  a  salt  and  water,  may  really  serve  to 
identify  a  particular  substance,  we  must  admit  that  there  are 
some  substances  such  as  sodium  hydroxide,  calcium  hydroxide, 
etc.,  which  everybody  agrees  to  call  bases,  and  when  one  of  these 
reacts  with  ian  unknown  substance  in  a  manner  similar  to  its  re- 
action with  a  well  recognized  acid,  then  the  unknown  substance 


66  University  of  Texas  Bulletin 

is  thus  recognized  to  be  an  acid;  and  the  corresponding  argu- 
ment is  applied  when  an  unknown  substance  reacts  with  a  sub- 
stance which  everybody  agrees  to  call  an  acid,  such  as  hydro- 
chloric or  sulphuric  acid.  All  other  descriptive  properties  con- 
cerning these  substances  are  not  essential  to  define  or  characterize 
them  as  acids,  bases  or  salts  respectively. 

In  the  experimental  demonstration  give  first  the  neutraliza- 
tion of  a  soluble  base  by  a  soluble  acid  with  the  aid  of  an  in- 
dicator; and  second  the  neutralization  of  a  soluble  acid  by  an 
insoluble  base.  For  instance,  add  copper  oxide  to  warm  dilute 
sulphuric  acid  until  some  of  the  insoluble  oxide  remains  un- 
acted upon,  then  concentrate  the  solution.  The  salt  will  crys- 
tallize out  on  cooling. 

All  acids,  bases  and  salts  are  binary  compounds.  This  should 
be  accepted  as  a  plain  fact,  without  any  discussion.  The  two 
kinds  of  constituent  parts  are  called  ions,  for  reasons  given 
later  on. 

At  this  point  it  is  advisable  to  enlarge  very  much  upon  the 
usual  treatment  of  Acids,  Bases  and  Salts  in  text  books.  For 
this  purpose  students  should  memorize  the  formulae  of  about 
eight  to  ten  basic  oxides  (e.  g.  Na20,  K20,  CaO,  CuO,  MgO, 
ZnO,  A1203,  Fe2O3),  as  well  as  the  formulae  for  a  num- 
ber of  acids  in  addition  to  those  already  met  with  before  (e.  g. 
HN03,  H3P04,  H2C03,  H2S04,  H2S03,  H  (C2H303). 

Next  in  order,  the  student  should  learn  to  r&cognize  the 
valence  of  the  metal  ions  or  of  the  acid  ions  from  the  formulae 
of  the  bases  or  acids  just  given.  Without  any  reference  to  the 
atomic  theory,  define  valence  as  follows:  "The  valence  of  an 
ion  (that  is,  one  of  the  two  kinds  of  parts  into  which  any  acid, 
base,  or  salt  primarily  divides)  is  the  number  of  H's  it  appears 
to  take  the  place  of,  or  to  combine  with,  as  shown  by  the  for- 
mulae of  different  compounds  on  comparison." 

Note  that  this  definition  presents  valence  as  a  numerical  re- 
lation shown  by  the  formula®  and  does  not  mention  the  word 
atom.  Reference  to  the  atomic  theory  is  thus  seen  not  to  be 
necessary;  though  there  is  no  objection  to  considering  valence 
as  a  property  of  atoms  or  groups  of  atoms  if  the  connection 
between  the  formulae  and  the  atomic  theory  of  matter  has  been 
pointed  out  before  this. 


Chemistry  in  High  Schools  67 

Next  in  order,  the  student  should  learn  how  the  metal  iona 
and  acid  ions  from  the  above  memorized  formulae  must  be  put 
together  in  accordance  with  the  demands  of  valence  in  order 
to  obtain  the  formulae  of  the  normal  salts.  This  should  be 
drilled  upon,  and  the  fundamentals  of  nomenclature  should  be 
given. 

Finally  drill  the  student  in  writing  equations  between  all 
the  acids  and  all  the  bases  which  have  been  memorized.  They 
are  &11  metathetical  reactions. 

Definition  of  the  metathetical  raction :  It  is  one  in  which  two 
binary  compounds  exchange  their  negative  parts  (or  their  posi- 
tive parts)  producing  only  two  new  compounds,  the  valences 
of  all  ions  remaining  constant  during  this  change.  Whenever 
two  substances  are  said  to  react  metathetically,  this  one  word 
tells  fully  what  takes  place:  with  this  knowledge,  anyone  is 
able  to  write  the  equation  of  a  change  if  he  knows  the  formulae 
of  the  substances  involved. 

Hydration  of  Oxides. 

1.  To  be  illustrated  with  the  slaking  of  quick  lime;  then 
follows  the  general  information: 

(a)  Basic  oxides  when  hydrated  usually  appear  as  hydrated  to 
the  maximum  extent,  that  is,  two  hydroxyls  are  formed  from  every 
0  in  the  formula  of  the  oxide,  e.   g.,   CaO+H,0=Ca(OH)2 
(drill  in  writing  such  equations  with  other  basic  oxides). 

(b)  When  placed  in  contact  with  water,  only  those  oxides 
the  hydroxides  of  which  are  soluble  actually  take  up  water  to 
form  hydroxides.    Of  the  common  hydroxides  only  those  of  the 
alkali  and  alkaline  earth  metals  are  soluble.     Drill! 

2.  The  hydroxides  of  metals  also  are  bases,  just  as  well   as 
the  oxides.     Drill  on  writing  all  the  equations  of  the  reactions 
between  the  hydroxides  of  the  eight  metals  (in  the  list  of  bases 
memorized  above)  with  the  acids  given  above. 

3.  Recall  the  fact  that  metals  form  basic  oxides  and  non- 
metals  form  acid  oxides.    The  latter  hydrate  just  as  well  as  the 
basic  oxides;  however,  the  extent  of  hydration  follows  no  rule, 
and  is  usually  less  than  the  maximum.    Common  acid  oxides  are-: 
S02,   S03,  C02,  P2O5,  N2O5  N208,      P203.     Drill    on   writing 


68  University  of  Texas  Bulletin 

the  relation  between  these  plus  water,  giving  the  ordinary 
acids,  (H2S03,  H2S04,  H2C03,  H3P04,  HN03,  HN02,  H3PO,). 
4.  The  actual  hydration  of  acid  oxides  on  contact  takes 
place  readily  with  nearly  all  acid  oxides  because  the  resulting 
acid  is  soluble  in  nearly  all  cases  (exceptions:  silicic  acid 
H2Si03.  from  Si02;  arsenious  acid,  HAs02,  from  As203). 

Solubility  of  Salts. 

By  solubility  is  meant  the  solubility  of  these  substances  in 
water,  not  their  solubility  in  a  solution  which  acts  on  them 
chemically.  None  of  these  substances  are  absolutely  insoluble; 
they  are  all  slightly  soluble  and  they  present  enormous  relative 
differences  in  their  actual  solubilities. 

A  short  table,  of  the  solubilities  of  the  ordinary  salts  such 
as  is  given  below,  should  be  committed  to  memory  by  the  stu- 
dent. 

Table  of  Solubilities  of  Salts. 

Nitrates  and  Acetates.     All  soluble. 

Sulphates.  All  soluble  except  PbS04,  BaS04,  SrS04,  and 
CaS04.  The  last  is  perceptibly  soluble. 

Chlorides.  All  soluble  except  AgCl,  HgCl,  PbCl2.  The  last  is 
slightly  soluble  in  cold  water,  and  quite  soluble  in  hot  water. 

Normal  Carbonates  and  Phosphates.  All  insoluble  except 
those  of  the  alkali  metals,  Na,  K  and  "NH4." 

The  solubilities  of  the  substances  is  one  of  the  largest  factors 
which  determine  whether  or  not  metathetical  reaction  will  take 
place.  Thus  even  in  the  reaction  between  a  base  and  an  acid, 
for  which  there  is  always  a  decided  tendency,  insolubility  will 
retard  the  action  somewhat  in  proportion  to  the  insolubility  of 
the  salt  formed,  and  may  prevent  it  practically  entirely.  The 
following  experimental  procedure  serves  to  show  this.  The  ex- 
periment is  an  excellent  one  to  develop  chemical  notions : 

Put  into  each  of  three  test-tubes  a  pinch  of  zinc  oxide,  and 
add  to  one  just  enough  dilute  HC1  so  that  when  the  mixture  is 
stirred  and  warmed  the  zinc  oxide  dissolves.  Treat  the  second 


Chemistry  in  High  Schools  69 

portion  of  zinc  oxide  with  HN03,  and  the  third  with  dilute 
H,S04.  In  the  same  way  try  calcium  oxide  (or  hydroxide), 
and  lead  oxide.  Do  you  observe  any  relation  between  the  sol- 
ubilities of  the  salts  that  are,  or  should  be,  formed,  and  the 
rate  at  which  reaction  takes  place? 

When  insoluble  salts  are,  or  would  be,  thus  formed,  is  there 
absolutely  no  action  or  is  the  action  merely  retarded?  To  find 
the  answer  to  this  question  examine  particularly  the  mixtures  of 
lead  oxide  with  HC1  and  H2S04,  respectively.  The  change  from 
yellow  oxide  to  white  salt  in  these  cases  will  reveal  whether  or  not 
any  action  takes  place.  If  you  conclude  that  the  action  is  merely 
retarded,  and  you  wish  to  find  an  explanation  of  this,  drop  a 
small  lump  of  marble  into  some  dilute  H2S04  and  observe  that 
a  copious  evolution  of  C02  takes  place  for  just  a  moment,  fol- 
lowed by  a  very  slow  action.  Take  out  the  piece  of  marble, 
scrape  off  the  outer  layer  and  drop  the  lump  into  dilute  H2SO4 
again.  Rapid  action  which  lasts  only  for  a  short  while  is  again 
observed.  It  is  evident  that  the  layer  of  insoluble  calcium  sul- 
phate formed  covers  the  lump  and  retards  the  diffusion  of  the 
acid  to  the  calcium  carbonate.  In  the  experiments  above,  the 
particles  are  much  smaller,  yet  the  actions  are  retarded  in  the 
same  way. 

Acid  Salts. 

With  due  consideration  of  what  the  ionisation  theory  teaches 
concerning  the  ionisation  of  polybasic  acids,  acid  salts  should 
be  treated  somewhat  as  follows:  when  an  acid  such  as. phos- 
phoric, H3P04,  separates  into  its  main  constituent  parts  (ions), 
at  first  only  one  H  separates,  leaving  the  remainder  intact  as  a 
monovalent  ion  ( H2P04 ) ' ;  and  when  the  first  portions  of  a 
base  are  added  to  a  solution  of  such  an  acid,  the  reaction  of 
neutralization  takes  place  as  though  this  were  a  monovalent 
acid,  the  composition  of  the  acid  radical  of  which  is  (H2P04) '. 
Hence  the  aluminium  salt  would  have  the  formula 
A1(H2P04)3. 

Note: — the  valence  of  metals  and  all  positive  ions  is  desig- 
nated with  an  asterisk — e.  g.  H* ;  that  of  acid  radicals  and  other 
negative  ions  by  an  apostrophe,  as  N03',  S04",  etc. 

After  enough  base  has  been  added  to  neutralize  all  of  the  first 


70  University  of  Texas  Bulletin 

set  of  H-ions,  then  the  second  H  ionizes  extensively  and  leaves 
the  bivalent  ion  (HPO4)  ";  hence  salts  formed  under  these  con- 
ditions appear  to  have  a  formula  similar  to  those  formed  with 
bivaJentacid  ions,  e.  g.,  A12(HPO4)3. 

After  the  second  hydrogen  has  been  neutralized,  then  the 
tendency  to  ionize  the  third  hydrogen  may  become  effectve, 
leaving  the  trivalent  ion,  (P04)'". 

Of  course  if  enough  base  is  added  all  at  once  to  neutralize 
more  than  one  or  two  H's  the  reaction  immediately  proceeds 
to  the  corresponding  extent.  Thus  if  a  drop  of  sulphuric  acid 
is  added  to  more  than  enough  of  sodium  hydroxide  solution  to 
neutralize  the  acid  completely,  then  the  salt  Na2S04  is  formed 
immediately;  but  when  the  procedure  is  reversed,  that  is,  when 
a  drop  of  sodium  hydroxide  solution  is  added  to  a  great  deal  of 
sulphuric  acid,  then  it  will  form  only  the  acid  salt  Na(HS04). 

That  the  (experimental)  formation  of  acid  salts,  with  poly- 
basic  acids,  depends  only  on  the  relative  proportions  of  acid 
and  bases  mixed  should  be  strongly  emphasized  and  drilled 
upon.  In  the  following  lessons  the  reactions  between  carbon 
dioxide  and  lime  water ;  and  the  passing  of  S02  into  sodium 
hydroxide  solution  until  no  more  is  absorbed — these  and  others 
furnish  excellent  examples  to  bring  out  this  same  point;  and 
this  reaction  also  furnishes  a  good  opportunity  to  develop  chem- 
ical notions  as  distinct  from  the  mere  arithmetic  notions  in- 
volved in  equation  writing. 

The  following  experiment  is  here  given  in  full  to  demonstrate 
the  actual  formation  of  acid  salts : 

"Secure  a  fresh  solution  of  tartaric  acid,  H2(C4H406),  con- 
taining about  200  grams  per  liter,  and  a  solution  of  potassium 
hydroxide  containing  about  150  grams  to  the  liter  and  fill  two 
burettes  with  these  solutions  respectively.  Measure  out  20  cc.  of 
potassium  hydroxide  solution  into  a  small  flask,  add  30  cc.  of 
the  tartaric  acid  solution  measured  from  the  other  burette,  then 
heat  the  mixture  to  the  boiling  point,  add  a  drop  or  two  of 
phenolphthalein  solution  and  finish  neutralizing  it  by  adding 
more  tartaric  acid  from  its  burette.  Cool  the  mixture  under  a 
jet  of  tap  water  and  add  to  it  as  much  tartaric  acid  again  as 
was  necessary  to  neutralize  the  potassium  hydroxide.  Crystals 
of  potassium  acid-tartrate  will  be  formed.  Next  heat  the  mixture 


Chemistry  in  High  Schools  71 

to  boiling  and  add  KOH  slowly,  with  constant  stirring  until  an 
amount  approximately  equal  to  the  original  amount  has  been 
added.  Note  that  the  crystals  dissolve  as  KOH  is  added.  Ex- 
plain what  happens  in  each  step  and  write  the  equations  of  the 
three  reactions ;  they  are  all  metathetical  changes.  Note  that  the 
second  portion  of  potassium  hydroxide  used  is  equal  to  the  first 
portion  used.  The  composition  of  the  crystals  that  separated 
from  the  solution  is  KH(C4H4O6),  potassium  acid-tartrate,  or 
potassium  bitartrate.  Give  reasons  for  both  names. 

Carbon. 

Present  some  of  the  properties  of  the  element,  the  discussion 
of  the  flame,  some  descriptive  matter  concerning  the  importance 
of  carbon  monoxide  on  account  of  its  presence  in  water  gas  and 
its  use  in  the  reduction  of  ores  (e.  g.  of  iron  ores). 

2.  Show  that  the  preparation  of  carbon  dioxide  from  prac- 
tically any  carbonate  is  in  general  similar  to  the  preparation  of 
HC1  (noting  however  the  difference  in  the  solubilities  of 
the  two  gases  and  that  carbon  dioxide  is  not  oxidizible;  hence 
almost  any  ordinary  acid  may  be  used  to  liberate  it  from  its 
salts).  Show  some  of  its  common  properties  and  emphasize 
that  the  portion  dissolved  in  water  is  largely  hydrated;  when- 
ever it  acts,  in  solution,  as  an  acid  on  a  base,  then  it  is  H2C03 
which  is  the  actually  acting  substance,  and  not  CO2.  A  sep- 
arate equation  should  always  be  written  to  express  the  hydra- 
tion  and  dehydration  that  may  precede  or  follow  a  metathet- 
ical reaction.  Thus  when  carbon  dioxide  is  absorbed  by  lime 
water  the  following  reactions  take  place  in  the  order  here  given: 

(a)  C02+H20=H2C03. 

(b)  H2C03+Ca(OH)2=CaCO3+2H20. 

These  reactions  should  not  be  combined  into  the  following  ex- 
pressions : 

C02+Ca(OH)2:=CaC03+H20.     (avoid  this!) 

Be  certain  to  make  the  experiment  of  passing  carbon  dioxide 
into  lime  water  until  the  solution  clears  up  again;  and  then 
boi!  the  solution.  The  student  should  know  this  experiment 
and  action  thoroughly,  and  also  know  its  application  in  nature 
and  in  the  production  of  boiler  scale  (temporary  hardness  of 
potable  water). 


72  University  of  Texas  Bulletin 

Sulphur. 

Deal  briefly  wtih  the  properties  of  the  element  (the  phenom- 
ena presented  by  melted  and  cooled  sulphur,  etc.,  need  not  be 
considered).  Emphasize  the  source  and  extraction  of  commer- 
cial spulphur. 

Deal  with  hydrogen  sulphide  very  briefly  here.  Make  some 
iron  sulphide  and  liberate  hydrogen  sulphide  from  it.  Note  that 
the  gas  is  poisonous.  The  reactions  involved  in  these  examples 
are  mainly  simple  or  metathetical,  and  the  complex  oxidation 
reactions  of  hydrogen  sulphide  must  be  omitted  here.  The  use 
of  hydrogen  sulphide  as  a  laboratory  reagent  will  be  sufficiently 
illustrated  later. 

Prepare  sulphur  dioxide  by  means  of  the  reaction  between 
sulphites  and  acids.  Point  out  that  the  method  in  general  is 
the  same  as  that  employed  for  the  production  of  carbon  dioxide 
and  of  HCL  The  student  should  learn  this  and  also  remember 
the  particular  substances  that  he  actually  handled  in  this  con- 
nection in  the  laboratory.  In  the  equations  involved,  the  ex- 
pression for  hydration  and  dehydration  should  be  separated 
from  the  metathetical  reactions — as  was  advised  for  carbon 
dioxide.  The  main  chemical  property  of  S02  (or  of  sulphurous 
acid)  is  its  tendency  to  be  oxidized  to  sulphuric  acid.  This  may 
be  illustrated  as  follows: 

Prepare  a  saturated  aqueous  solution  of  S02.  Put  a  little  of 
it  in  a  test  tube,  add  a  few  drops  of  hydrochloric  acid  and  a  drop 
or  two  of  barium  chloride  solution.  Only  a  slight  or  negligible 
precipitate  will  be  formed.  Now  add  to  the  main  portion  of 
the  solution  one  or  two  cc.  of  concentrated  nitric  acid  and  heat 
gently  to  boiling.  Some  brown  fumes  of  oxides  of  nitrogen 
will  be  formed  to  a  slight  extent,  which  show  that  the  nitric  acid 
has  acted  as  an  oxidizing  agent.  Now  test  the  solution  again 
with  barium  chloride  previously  acidified  with  a  few  drops  of 
HC1.  A  copious  precipitate  of  barium  sulphate  will  be  ob- 
tained. This  test  depends  upon  the  fact  that  barium  sulphite 
is  soluble  in  this  mixture  while  barium  sulphate  is  not;  hence 
not  until  the  sulphurous  acid  is  changed  to  sulphuric  will  a 
precipitate  be  formed. 

The  commercial  production  of  sulphuric  acid  by  the  contact 


Chemistry  in  High  Schools  73 

method  may  be  given  here.  If  the  old  English  method  is  given, 
no  reference  need  be  made  to  the  formation  of  nitrosyl  sul- 
phuric acid.  It  is  perfectly  correct  to  state  that  NO  takes  up 
oxygen  to  form  N02  and  this  change  takes  place  more  readily 
and  hence  faster  than  the  direct  reaction  between  S02  and  the 
oxygen  of  the  air.  The  oxides  of  nitrogen  are  merely  catalytic 
agents,  and  the  impelling  tendency  of  the  action  is  always  the 
tendency  of  S02  to  take  up  oxygen. 

Ammonia. 

Stress  the  commercial  source  of  ammonia;  its  liberation  from 
the  salts  by  a  general  method  which  corresponds  to  the  general 
method  for  the  liberation  of  carbon  dioxide,  HC1,  and  SO2, 
Any  ammonium  salt  and  any  base  may  serve  for  this  purpose 
although  the  reaction  takes  place  readily  only  with  a  strong 
(soluble)  base.  Stress  the  fact  that  ammonia  hydrates  readily 
— otherwise  the  usual  treatment  found  in  texts  may  be  given. 

Other  Optional  Topics. 

The  following  topics  may  be  treated  here  at  the  option  of  the 
teacher : 

1.  The  liberation  of  nitric  acid  from  its  salt, — but  do    not 
consider  at  this  point  the  production  of  oxides  of  nitrogen,  or 
the  reaction  of  nitric  acid  with  metals,  etc. 

2.  The  other  halogens:  fluorine,  bromine  and  iodine. 

For  fluorine  the  etching  effect  of  hydrofluoric  acid  upon  glass 
is  the  only  experiment  to  be  given.  For  bromine  and  iodine, 
show,  with  test  tube  trials,  the  liberation  of  HBr  and  HI  from 
their  salts  by  means  of  phosphoric  acid  (do  not  use  sulphuric), 
and  then  show  the  liberation  of  the  elements  from  these  acids  by 
means  of  an  oxidizing  agent  (add  powdered  Mn02  to  the  mix- 
tures in  the  test  tubes)  :  The  displacement,  by  chlorine,  of  bro- 
mine from  bromides  and  of  iodine  from  iodides,  should  also  be 
presented  here. 

lonisation  and  the   General  Relation  Between  Dissolved  Sub- 
stances Which  Results  in  Metathetical  Reaction* 
This  topic  should  be  begun  by  showing  experimentally  some 
fundamental  facts  concerning  electrical  conductivity  of    so!u- 


*Read  pages  47-49  in  this  connection. 


74  University  of  Texas  Bulletin 

tions.  This  may  be  shown  most  conveniently  by  means  of  an 
alternating  electric  light  current  and  an  incandescent  lamp. 
Cut  one  of  the  two  wires  of  an  "extension  cord"  and,  to  the  two 
ends  thus  obtained,  attach  platinum  wires  for  electrodes.  Dip 
the  latter  into  a  beaker  filled  with  distilled  water,  attach  the 
plug  to  the  light  circuit,  and  insert  the  lamp  into  the  socket  of 
the  cord.  It  will  be  found  that  distilled  water  does  not  conduct 
the  current  sufficiently  well  to  light  up  the  lamp.  Next  pour 
a  little  hydrochloric  acid  into  the  water:  the  lamp  will  burn 
brightly,  which  shows  that  this  solution  conducts  well.  Repeat 
with  fresh  water  and  acetic  acid:  the  lamp  will  burn  dimly, 
which  shows  that  the  solution  conducts  poorly.  In  the  same  way 
try  sodium  hydroxide  solution,  ammonium  hydroxide  solution, 
alcohol  in  water,  and  various  salt  solutions.  These  experiments 
suffice  to  dispose  the  student  favorably  to  receive  the  following 
general  facts. 

Acids,  bases,  and  salts,  when  dissolved  in  water  dissociate 
into  parts,  called  ions,  each  of  which  carries  a  definite  number 
of  positive  or  negative  unit  charges,  the  number  of  which  cor- 
responds to  the  valence.  Metals  and  hydrogen  carry  positive 
charges,  while  the  non-metals,  acid  radicals,  and  the  hydroxyl 
radical  carry  negative  charges. 

Not  all  of  an  acid,  base,  or  salt  in  a  solution  is  present  in  the 
form  of  ions.  A  part  is  present  in  the  undissociated  or  com- 
bined form.  This  is  due  to  the  tendency  of  ions  to  recombine. 
These  two  opposing  tendencies,  of  ionisation  and  of  recombina- 
tion, hold  each  other  in  equilibrium  when  a  certain  fraction  of 
the  dissolved  substance  is  in  the  form  of  ions  and  undissociated 
part,  respectively.  These  fractions  have  different  values  with 
different  substances,  and  the  "ion"  fractions  increase  with  dilu- 
tion, while  the  undissociated  decrease. 

The  following  general  statement  covers  the  degrees  of  disso- 
ciation of  all  common  substances.  It  should  be  committed  to 
memory : 

All  normal  salts,  all  strong  acids  (hydrochloric,  nitric,  sul- 
phuric), all  strong  bases  (that  is,  all  soluble  bases  except  am- 
monia) ionize  extensively  in  aqueous  solutions. 

All  weak  acids  (acetic,  carbonic,  sulphurous,  phosphoric), 
all  weak  bases  (ammonia)  and  water  itself,  are  very  slightly 
dissociated  (about  1%  and  much  less)  in  aqueous  solutions. 


Chemistry  in  High  Schools  75 

Insoluble  or  very  slightly  soluble  substances  can  not  form  many 
ions  in  solution  and  hence  should  be  included  here  as  slightly 
dissociated  substances. 

The  chemical  activity  of  acids,  bases,  and  salts  depends  upon 
the  concentration  of  their  ions;  in  other  words,  it  is  primarily 
the  ions,  rather  than  the  undissociated  portions,  which  take  part 
in  chemical  reactions.  This  is  suitably  illustrated  by  means 
of  the  rates  of  action  of  hydrochloric  acid  upon  zinc,  and  of 
acetic  acid  upon  zinc,  or  the  rates  of  action  of  these  acids  upon 
marble,  all  of  which  is  readily  shown  by  means  of  test-tube  trials. 

The  fact  that  a  dissolved  acid,  base,  or  salt  is  present  in  solu- 
tion in  two  forms,  either  one  of  which  tends  to  change  to  the  other 
one  until  they  hold  each  other  in  equilibrium, — this  fact  appears 
strange  to  the  beginner,  and  yet  it  is  similar  to  the  familiar 
phenomenon  of  a  salt  dissolving  in  water  until  the  solution  is 
saturated,  and  hence  it  is  in  equilibrium  with  the  solid  salt;  it 
is  also  similar  to  the  evaporation  of  a  liquid  until  its  saturated 
vapor  is  in  equilibrium  with  it.  However,  there  is  one  essen- 
tial difference  between  these  equilibria  and  the  equilibrium  be- 
tween a  salt  and  its  ions,  namely,  there  are  always  two  kinds  of 
ions,  and  neither  one  kind  alone  can  hold  the  equilibrium  with 
the  undissociated  salt.  Both  must  be  present,  but  their  amounts 
or  numbers  per  cc.  necessary  for  any  one  state  of  equilibrium 
need  not  be  equal, — only  the  product  of  these  numbers  per  cc. 
must  remain  the  same.  Thus,  if  10  H  ions  and  10  acetate  ions 
(per  cc.)  are  present  in  a  certain  solution  (and  hence  holding 
in  equilibrium  the  undissociated  acetic  acid  present)  then  this 
equilibrium  would  also  be  held  by  1  H  ion  with  100  acetate 
ions  (99  of  them  from  another  acetate),  or  by  1  acetate  ion  with 
100  H  ions  (99  from  another  acid),  because  in  all  three  in- 
stances the  product  would  amount  to  100.  In  other  words,  the 
effect  of  the  ions  in  the  equilibrium  relation  with  their  compound 
is  measured  by  the  ion-product* 

The  following  experiment,  which  involves  exactly  the  same  re- 
lation, demonstrates  its  operation  in  the  simplest  manner. 

Prepare  one-half  test  tube  full  of  a  cold  saturated  solution 

*This  relation  does  not  hold  exactly  with  greatly  dissociated  acids, 
bases,  or  salts;  but  even  with  these,  the  fundamental  relation  is  prob- 
ably the  same,  and  hence  the  illustration  serves  for  all. 


76  University  of  Texas  Bulletin 

of  naphthalene  in  absolute  alcohol  and  one-half  test  tube  full 
of  a  cold  saturated  solution  of  picric  acid.  Pour  into  a  small 
(clean  and  dry)  flask  one-half  of  the  clear  saturated  solution  of 
picric  acid  and  two-thirds  as  much  of  the  naphthalene  solution, 
the  two  quantities  being  gauged  as  accurately  as  possible  with 
the  eye.  They  unite  to  form  naphthalene  picrate,  designated 
by  NP.  This  solution  and  all  others  in  this  experiment  must 
be  kept  cool, — they  should  not  be  warmer  than  18  degrees  C. 
Allow  the  mother  liquid  to  drain  from  these  crystals,  and  pre- 
pare a  saturated  solution  of  NP  by  adding  a  small  portion  of 
absolute  alcohol,  shaking  the  mixture  vigorously,  and  repeating 
this  treatment  until  most  of  the  crystals  (not  all !)  have  dissolved. 
To  o/ne-half  of  this  solution  add  one-eighth  as  much  (by  volume) 
of  the  remaining  clear  picric  acid  solution.  Some  of  the  com- 
pound NP  should  separate  from  the  solution.  To  the  other  half 
of  the  saturated  NP  solution  add  one-eighth  as  much  of  the 
clear  naphthalene  solution.  Again  some  of  the  compound  NP 
should  separate  from  the  solution. 

Since  in  one  test-tube  full  of  solution  of  N  P,  the  addition 
pf  N  resulted  in  the  formation  of  more  of  the  compound,  there 
must  have  been  some  (free)  picric  acid  in  this  solution;  and 
since  in  the  other  test-tube  full  of  this  solution  the  addition  of 
P  resulted  also  in  the  formation  of  more  of  the  compound,  it 
follows  that  the  solution  also  contained  some  (free)  naphtha- 
lene. Hence  the  solution  contains  both  free  N  and  free  P  be- 
sides the  compound  NP.  The  effect  of  the  free  N  and  free  P 
upon  the  equilibrium  with  their  compound  NP  is  measured  t>y 
the  product  of  their  numbers  per  cc.,  say  aXb  (if  a  is  the  num- 
ber of  N  per  cc.  and  b  is  the  number  of  P).  When  a  is  increased 
by  adding  a  little  of  the  saturated  solution  of  naphthalene, 
then  aXb  is  increased  and  the  equilibrium  disturbed.  In  order 
to  regain  equilibrium,  some  of  the  free  N  and  free  P  combine, 
thus  reducing  a  and  b  until  aXb  reaches  its  former  value  again; 
and  this  newly  formed  NP  separates  from  the  solution  because 
the  latter  is  saturated  with  NP.  The  corresponding  change  takes 
place  when  picric  acid  is  added. 


Chemistry  in  High  Schools 


77 


Inches  —  Inside- 


D.C 
Main. 


Rheostat 


Conductivity  Trough  and  Connections 


78  University  of  Texas  Bulletin 

In  order  to  demonstrate  the  determination  of  the  per  cent  of 
dissociation  in  electrolytes  it  is  better  to  use  the  conductivity 
method  rather  than  others  such  as  a  freezing  point  method,  be- 
cause the  connection  between  the  experiment  and  the  notion  to 
be  demonstrated  is  more  direct.  The  following  experimental 
arrangement  makes  the  procedure  extremely  simple.  This  ex- 
periment also  serves  to  demonstrate  that  the  degree  of  ionisation 
of  a  dissolved  substance  increases  with  dilution. 

Have  a  carpenter  make  a  wooden  vessel  of  the  shape  and  di- 
mensions given  in  Fig.  8.  Stout  cypress  or  soft  pine  boards,  at 
least  ly^  inch  thick  and  perfectly  smooth  on  both  sides,  are  to 
be  used.  The  vessel  should  be  as  nearly  water  tight  as  the  car- 
penter can  make  it.  It  should  then  be  thoroughly  covered  on 
the  inside  wilth  melted  paraffin  to  make  it  absolutely  water 
tight,  and  in  order  that  the  boards  may  not  take  up  any  of  the 
solutions  poured  in  it.  Now  secure  from  a  plumber  or  cornice 
maker  a  piece  of  fairly  stiff  sheet  copper,  at  least  16  inches 
square.  Cut  it  from  one  corner  diagonally  across  to  the  oppo- 
site corner  into  two  triangular  pieces.  Trim  each  piece  if  nec- 
essary, so  that  each  sheet  of  copper  may  cover  exactly  one  of 
the  triangular  ends  of  the  trough.  Bend  over  the  excess  of 
each  plate  at  the  top,  arid  clamp  or  place  each  copper  plate  so 
that  it  may  stick  closely  to  the  wooden  end  of  the  trough  it 
covers.  Provide  any  suitable  means  for  connecting  the  copper 
sheets  to  the  wires  of  an  electric  circuit.  Shake  up  about  200 
grams  of  crystals  of  copper  nitrate  with  about  200  cc.  of  water 
until  a  saturated  solution  is  obtained.  Take  about  100  cc.  of 
this  solution  and  pour  it  into  the  trough.  (1)  Secure  an  am- 
meter with  a  total  capacity  of  1  or  only  a  few  amperes, 

(2)  a  volt-meter  with  a  capacity  of  3  volts  or  only  a  little  more, 

(3)  a  source  of  direct  electric  current  with  a  voltage  of  2  to  10 
volts,  and  (4)  a  rheostat  of  such  capacity  and  construction  that 
the  current  used  in  this  experiment  may  be  controlled  to  within 
0.01  ampere.     Connect    up    all   this  apparatus  and  the  trough 
as  shown  in  Fig.  9.     Turn  on  the  current  and  adjust  it  with  a 
rheostat  until  it  is  1-5  or  1-6  of  the  total  that  the  ammeter  can 
carry,  but  not  exceeding  %  ampere.     Note  both  ammeter  and 
voltmeter  readings  that  are  then  shown.     In  the  following  op- 
erations adjust  the  current  so  that  the  first  voltage  between  the 


Chemistry  in  High  Schools  79 

poles  (which  the  voltmeter  indicated)  is  kept  constant,  and 
record  in  parallel  columns  the  amount  of  current  that  flows 
after  each  dilution  of  the  solution.  Dilute  the  solution  by  add- 
ing measured  amounts  of  distilled  water:  at  first  in  portions 
of  100  cc.  at  a  time,  subsequently  in  larger  portions  of  sev- 
eral 100  cc.  At  the  beginning,  the  increase  in  current  will 
be  relatively  large  with  each  addition  of  water;  then  it  will  be- 
come less  until  finally  no  further  increase  in  current  is  obtained. 

Divide  the  final  (maximum)  value  into  the  first  value  (ob- 
tained with  the  original  solution)  :  this  gives  the  fraction  of 
the  salt  present  as  ions  in  the  original  solution. 

The  larger  current  obtained  after  dilution  shows  that  the  num- 
ber of  ions  arriving  at  the  poles  each  second  is  larger  after  dilu- 
tion than  before.  Since  the  attractive  force  (voltage)  is  kept  con- 
stant and  hence  the  ions  move  at  the  same  speed,  and  since  on 
dilution  they  are  moved  parallel  to  the  poles  but  remain,  as  a 
whole,  at  the  same  perpendicular  distances  from  them,  there 
remains  no  other  way  to  account  for  the  greater  number  of  ions 
arriving  at  the  poles  after  dilution  except  the  conclusion  that  the 
number  of  ions  is  increased  with  dilution  until  all  the  ions  pos- 
sible have  been  formed. 

Point  out  next  the  general  conditions  under  which  metathet- 
ical  reactions  take  place,  and  apply  this  to  the  neutralization 
of  an  acid  with  a  base  and  to  the  experiments  given  below.  The 
following  outline  may  be  helpful  here. 

(a)  Whenever  two  solutions  (or  a  solution  and  a  slightly  sol- 
uble solid)   are   mixed,    the    (accidental)    meeting    of   the    ca- 
tions from  one  solution  with  the  anions  from  the  other  solution 
will  produce  at  least  small  amounts  of  all  the  new  compounds 
possible. 

(b)  Note  the  amount    (in  a  general  way,  that  is,  whether 
large  or  small)  of  each  free  ion  in  the  mixture  at  the  beginning. 

(c)  Note  the  amount  (i.  e.  large  or  small)  of  free  ions  that 
can  be  produced  by  each  of  the  resulting  substances.     This  is 
the  amount  of  its  ions  with  which  each  one  would  be  in  equilib- 
rium,— this  is  very  small  in  the  case  of  slightly  soluble  and 
slightly  dissociated  substances.* 

*To  be  exact,  we  should  consider  here  the  product  aXb,  of  the  con- 
centrations of  each  pair  of  ions  in  place  of  their  amounts  (see  page  75). 


80  University  of  Texas  Bulletin 

(d)  If  an  insoluble  or  slightly  dissociated  substance  is  among 
the  resulting  ones,  and  the  amount  of  its  ions  in  the  original 
mixture  is  much  larger  than  the  small  amount  with  which  it 
would  be  in  equilibrium,*  then  this  pair  of  free  ions  will  com- 
bine and  thus  they  will  reduce  their  amounts  until  these  are 
small  enough  for  equilibrium.  As  thus  the  free  ions  disappear, 
any  undissociated  portions  of  their  original  compounds  will 
ionize  and  be  used  up  in  turn. 

If  one  of  the  original  substances  is  only  slightly  soluble 
(as  in  d  below),  then  at  first  it  will  dissolve  only  in  the  small 
amount  which  saturates  the  solution.  Then  as  the  amount  in 
solution  is  changed  by  reaction,  more  solid  will  dissolve,  and 
so  on. 

All  metathetical  reactions  are  due  to  such  extensive  reduc- 
tion of  the  original  number  of  a  certain  pair  of  ions.  A  slight 
formation  of  a  new  compound,  by  ions  combining  to  a  slight 
extent,  is  not  considered  to  be  a  reaction. 

The  student  should  make  test-tube  trials  with  the  following 
mixtures,  and  point  out  in  each  case  the  particular  pair  of  ions 
which  by  combining  extensively  serve  in  a  sense  as  the  primary 
cause  of  the  reaction: 

(a)  Mix  any  one  of  several  barium  salt  solutions  with  any 
one  of  several  sulphates,   producing  in  this  way  barium  sul- 
phate from  at  least  nine  different  mixtures. 

(b)  Produce  silver  chloride  from  several  different  mixtures. 

(c)  Produce  ferric  hydroxide  from  several  different  mix- 
tures. 

(d)  Dissolve  calcium  phosphate  in  dilute  hydrochloric  acid. 
Here  the  least  ionized  combination  is  a  combination  of  H  ions 
with  P04  ions,  for    instance,    (H2P04) ',    the  calcium  salt    of 
which  acid  radical  is  soluble. 

(e)  To  the  mixture  obtained  in  (d),  add  ammonia  to  neu- 
tralize the  acid.    The  ammonium  phosphate  thus  produced  will 
introduce  many  P04  ions,  and  calcium  phosphate  will  be  ob- 
tained as  a  precipitate. 

(f)  Add  solution  of  sodium  carbonate  to  an  aqueous  solu- 

*Or,  to  be  exact,  the  original  amounts  of  its  ions  form  a  larger 
ion-product  than  that  with  which  the  insoluble  or  slightly-dissociated 
substance  can  be  in  equilibrium. 


Chemistry  in  High  Schools  81 

tion  of  the  salt  of  any  metal  that  forms  insoluble  carbonates. 
Filter  and  dissolve  the  precipitate  by  means  of  the  addition  of 
any  acid  that  forms  a  soluble  salt.  Repeat  with  the  salts  of  five 
other  such  metals. 

These  experiments  enable  the  student  to  see  that  whenever  he 
knows  the  general  relations  between  the  ionized  substances  in 
a  given  mixture,  then  he  may  predict  whether  or  not  reaction 
will  take  place. 

Exercise. 

Which  of  the  substances  given  below  when  mixed  will  react? 
give  a  reason  for  your  answer. 

1.  Lead  oxide  and  water. 

2.  Barium  oxide  and  water. 

3.  Calcium  carbonate   and  hydrochloric   acid. 

4.  Sodium  acetate  solution  and  hydrochloric  acid. 

5.  Copper  sulphate  and  sodium  phosphate  solution. 

6.  Since  dry  sodium  chloride  and  concentrated  phosphoric 
acid  react  to  form  HC1  by  metathesis,  what  are  likely  to  be  the 
ionisation  relations  in  this  liquid  medium   (concentrated  phos- 
phoric acid)  to  bring  about  this  change? 

7.  If  the  liquid  medium  in  (6)   is  changed  by  the  addition 
of  much  water,  will  any  reaction  take  place  extensively?    What 
are  the  ionisation  relations  in  this  latter  case. 

Other  questions  of  similar  character  may  ~be  added. 

Electrolysis. 

The  first  experiment  to  be  given  is  the  electrolysis  of  hydro- 
chloric acid,  and  this  should  be  carried  out  with  the  following 
apparatus:  Secure  two  small  porous  cups,  3  to  4  inches  high 
and  V/2  to  2  inches  in  diameter.  Dip  the  upper  edges  to  a 
depth  of  one  inch  into  melted  paraffin  in  order  to  close  up  the 
pores  in  that  portion  of  the  cup.  Fit  rubber  stoppers  to  the 


82  University  of  Texas  Bulletin 

cups.  Through  each  stopper  cut  two  holes, — one  to  fit  a  piece 
of  retort  carbon,  the  other  to  fit  the  glass  tubing  with  which  the 
apparatus  is  to  be  connected.*  Secure  also  a  porcelain  jar 
4  or  5  inches  in  depth  and  5  or  6  inches  in  diameter  in 
which  the  porous  cups  are  to  be  placed:  This  jar  is  to  be 
filled  with  a  saturated  salt  solution.  Secure  a  tall,  slender 
bottle,  of  at  least  one  quart  capacity,  fit  it  with  a  rubber  stop- 
per and  two  glass  tubes  one  of  which  extends  to  the  bottom  of 
the  bottle  while  the  other  terminates  just  below  the  stopper. 
In  place  of  this  bottle,  the  cylinder  shown  in  Fig.  10  may  be 
used.  This  bottle  or  cylinder  serves  to  retain  the  chlorine, 
and  allows  an  equal  volume  of  air  to  be  discharged  in  place 
of  the  chlorine.  Air  may  be  collected  over  water  without  ap- 
preciable loss,  while  chlorine  cannot  be  collected  over  water 
because  it  is  too  soluble.  Glass  tubes  for  connections  should 
now  be  bent  as  shown  in  Fig.  10.  The  tube  fitted  to  the 
cup  on  the  left  should  have  no  rubber  joints  in  it,  because 
hydrogen  is  to  be  evolved  at  this  pole,  and  this  gas  would  dif- 
fuse through  the  rubber  tubing  joints,  and  thus  vitiate  the  ex- 
periment. The  ends  of  the  delivery  tubes  which  are  to  be 
placed  under  the  burettes  should  be  drawn  out  to  a  small  open- 
ing. Secure  two  burettes  and  two  dishes  or  beakers  full  of 
water.  Place  the  burettes  in  position  with  the  lower  ends  ex- 
tending into  the  water,  and  fill  them  by  drawing  up  water  by 
means  of  a  piece  of  rubber  tubing.  By  this  means  they  may  be 
quickly  refilled  when  the  experiment  is  to  be  repeated.  For 
electric  connection,  twist  some  bare  copper  wire  around  two 
arc  light  carbon  rods,  insert  these  through  the  rubber  stoppers 
into  the  porous  cups,  and  connect  the  copper  wire  with  the  ter- 
minals of  an  electric  circuit  which  supplies  direct  current  at 
a  voltage  of  10  to  25  volts.  The  electrode  on  the  right  should 
be  connected  to  the  positive  terminal.  Insert  a  switch  in  the 
circuit  with  which  the  current  may  be  conveniently  turned  on 
or  off. 

Fill  the  porous  cups  three-fourths  full  of  a  mixture  of  equal 

*For  cutting  holes  in  rubber  stoppers,  sharpen  the  edge  of  a  cork 
borer  by  means  of  a  file,  thus  producing  a  rough  saw-like  edge  which 
is  very  effective,  dip  the  end  of  the  borer  into  caustic  soda  solution  or 
into  alcohol  and  proceed  as  with  cork  stoppers. 


Chemistry  in  High  Schools 


83 


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84  University  of  Texas  Bulletin 

parts  of  concentrated  hydrochloric  acid  and  .water.  To  the 
cup  on  the  right  add  a  few  crystals  of  potassium  permangan- 
ate. By  this  means  the  liquid  is  immediately  saturated  with 
chlorine.  Now  join  up  the  apparatus,  and  turn  on  the  cur- 
rent, but  allow  the  gases  discharged  by  the  delivery  tubes  to 
escape  into  the  air  and  not  collect  in  the  burettes.  After  elec- 
trolysis has  been  in  progress  for  a  minute  or  two  interrupt 
the  current,  place  the  burettes  over  the  openings  of  the  de- 
livery tubes  and  turn  the  current  on  again.  It  will  be  found 
that  the  two  gases  are  evolved  at  equal  rates  by  volume. 

Replace  the  hydrochloric  acid  in  the  cathode  (negative  pole) 
cup  by  dilute  sulphuric  acid,  and  turn  the  curent  on  again, 
i.e.,  repeat  the  experiment  with  the  two  cups  thus  filed  with 
different  solutions. 

Take  the  apparatus  apart  and  place  the  porous  cups  in  dis- 
tilled water  to  leach  out  the  solution  contained  in  the  pores. 
Salts  crystallizing  in  the  pores  would  crack  the  jars. 

The  last  experiment  indicates  that  the  fact  that  hydrogen  and 
chlorine  are  obtained  in  equal  volumes  cannot  be  due  to  any  ' '  de- 
composing" of  hydrochloric  acid  because  this  substance  is  present 
at  the  chlorine  pole  only,  and  the  hydrogen  liberated  is  certainly 
not  obtained  from  the  hydrochloric  acid  because  practically  no 
hydrogen  passes  through  the  intervening  salt  solution — a  fact 
that  could  be  easily  demonstrated. 

Before  taking  up  the  theory  of  the  changes  in  this  electro- 
lytic cell,  it  is  necessary  to  present  the  views  held  at  present 
concerning  the  nature  of  electricity.  "Electrical  matter'*  is 
considered  to  be  made  up  of  definite  unit  charges,  or  particles 
of  definite  size.  Electrically  neutral  substances  contain  an 
equal  number  of  positive  and  negative  unit  charges,  while 
ions  contain  an  excess  of  positive  or  negative  charges  corre- 
sponding to  their  valence. 

Only  negative  charges  are  mobile,  and  may  move  from  one 
material  particle  to  another,  or  from  one  kind  of  matter  to 
another.  These  mobile  negative  charges  are  called  electrons. 
The  positive  charges  are  fixed  upon  each  particular  particle 
of  mater,  and  are  never  transferred  from  one  particle  to  an- 
other. 


Chemistry  in  High  Schools  85 

In  accordance  with  this  theory,  the  change  at  the  cathode 
takes  place  as  follows:  the  electromotive  force  of  the  battery 
forces  electrons  to  pass  from  the  cathode  to  those  hydrogen 
ions  which  are  next  to  the  surface  of  the  cathode  (negative 
pole)  thus  changing  these  ions  to  neutral  hydrogen, — i.  e.  or- 
dinary, gaseous  hydrogen.  During  the  same  period  of  time, 
an  equal  number  of  chlorine  ions  which  are  next  to  the  sur- 
face of  the  anode  (positive  pole)  give  up  their  negative  charges 
or  electrons  to  the  pole,  thus  changing  to  neutral  chlorine  or 
ordinary  gaseous  chlorine. 

Since  a  drop  of  any  solution  is  electrically  neutral  to  the  out- 
side it  follows  that  it  must  contain  as  many  ions  with  postive 
charges  as  it  contains  ions  with  negative  charges.  When  ions 
are  discharged  at  the  cathode,  the  drops  of  liquid  which  have 
lost  the  cations  are  momentarily  left  with  an  excess  of  negative 
charge  while  the  opposite  state  of  affairs  exists  simultaneously 
at  the  anode.  These  drops  at  the  extreme  end  act  upon  their 
neighbors  so  as  to  obtain  from  them  the  kinds  of  ions  that  are 
necessary  to  re-establish  their  electric  neutrality.  This  action 
communicates  itself  from  drop  to  drop,  from  one  pole  to  the 
other,  and  results  in  a  slight  shift  of  all  the  positive  ions  to- 
ward the  cathode  and  all  the  negative  ions  toward  the  anode, 
as  a  result  of  which  all  the  drops  of  solution  regain  .their  elec- 
tric neutrality.  With  the  discharge  of  the  next  ions  at  the 
poles,  this  action  again  takes  place  and  so  on. 

These  are  the  essentials  that  have  to  be  brought  out  in  con- 
nection with  electrolysis.  The  writer  realizes  that  this  treat- 
ment is  very  dogmatic,  and  that  there  has  been  no  attempt 
made  to  show  why  scientists  have  arrived  at  the  fundamental 
notions  which  are  involved  her,  but  he  believes  that  the  young 
mind  is  scarcely  ready  to  follow  the  experimental  evidence. 

However,  it  must  be  emphasized  that  the  fundamental  no- 
tions presented  above  are  very  important,  and  should  be  taught 
in  the  manner  in  which  they  are  presented  here. 

The  following  further  experimental  demonstrations  of  elec- 
trolysis should  now  be  brought  before  the  students. 

Make  a  10  or  15  per  cent  solution  of  zinc  chloride,  and 
fill  two  porous  cups  with  this  solution.  As  before)  place  the 
two  cups  in  a  jar  filled  with  salt  water,  and  into  one  place 


86  University  of  Texas  Bulletin 

a  carbon  rod  for  an  anode,  and  into  the  other  a  strip  of  sheet 
copper  for  a  cathode,  but  leave  the  cups  open — i.  e.  unstop- 
pered.  Make  the  necesary  electrical  connections  and  pass  a 
current  through  this  cell.  Zinc  will  be  deposited  at  the  cathode, 
and  will  show  itself  by  its  gray  color;  while  chlorine  will  be 
evolved  at  the  anode  and  will  reveal  itself  by  its  odor. 

Replace  the  zinc  chloride  in  the  cathode  (negative  pole)  cup 
by- a  copper  sulphate  solution,  insert  a  clean  sheet  copper  pole 
and  turn  on  the  current  again.  Copper  will  be  deposited  upon 
the  cathode,  while  the  reaction  at  the  anode  is  the  same  as  before. 

Show  next  the  electrolysis  of  dilute  sulphuric  acid,  using 
either  the  apparatus  used  above  for  the  electrolysis  of  hydro- 
chloric acid,  or  a  Hoffmann  apparatus  (see  page  53  with  ref- 
erence to  the  purchase  of  the  latter.) 

Next  fill  the  same  apparatus  with  a  solution  of  sodium  sul- 
phate in  place  of  sulphuric  acid  and  show  that  when  this  solu- 
tion is  electrolyzed,  hydrogen  and  oxygen  are  liberated  in  the 
same  proportion  by  volume  as  with  sulphuric  acid.  Do  not  at- 
tempt to  force  a  large  current  through  this  solution  because  it  is 
a  poor  conductor,  and  the  heat  effect  of  the  current  is  liable  to 
crack  the  apparatus  at  the  electrodes. 

Then  secure  two  clean  porous  cups,  the  pores  of  which  contain 
neither  an  acid  nor  an  alkali.  Fill  them  with  a  solution  of  sodium 
sulphate,  insert  platinum  electrodes,  and  pfece  the  cups  in  a 
salt  water  jar  as  before.  Before  the  current  is  turned  on,  show 
with  the  aid  of  litmus  paper  that  the  solution  in  the  cups  con- 
tains neither  an  acid  nor  an  alkali.  Then  turn  on  the  current, 
and  show  that  the  solution  in  the  cathode  cup  becomes  alkaline 
and  the  solution  in  the  anode  cup  becomes  acid  as  the  result  of  the 
passing  of  the  current. 

Replace  the  liquid  in  the  cathode  cup  by  a  dilute  solution  of 
copper  sulphate,  and  show  that  copper  is  deposited  when  the 
current  is  passed  through  this  apparatus. 

These  experiments  show  that  the  nature  of  a  chemical  change 
at  a  pole  during  electrolysis  is  determined  by  the  nature  of  the 
substances  present  right  at  the  pole,  and  that  it  is  not  depend- 
ent upon  the  nature  of  the  substances  present  at  the  other  pole 
or  anywhere  else. 

The  electrolytic  discharge  of  the  ions  zinc,  copper,  hydrogen, 


Chemistry  in  High  Schools  87 

and  chlorine,  requires  no  further  explanation ;  but  the  discharge 
of  hydrogen  out  of  the  solution  of  a  sodium  salt  and  of  oxygen 
out  of  a  solution  of  a  sulphate  require  further  consideration. 
For  an  understanding  of  these  phenomena,  the  following  funda- 
mental or  general  facts  must  be  recognized: 

1.  Water  and  all  aqueous  solutions  contain  the  ions  of  water 
(i.  e.  hydrogen  and  oxygen  ions  practically),  and  although  the 
amounts  of  these  ions  present  are  small,  yet  if  they  are  ever 
used  up,  more  will  be  formed  as  fast  as  the  others  are  used  up. 

2.  If  two  or  more  different  ions  which  may  be  discharged 
are  present  at  a  pole,  that    particular  one  will    be    discharged 
which  will  set  up  the  least  opposing  electromotive  force  after  its 
discharge.     In  this  connection  see  page  91,  and  also  page  112. 
In  other  words,  the  ion  discharged  is  the  one  requiring  the  least 
voltage  for  its  discharge. 

With  these  two  fundamental  facts  the  discharge  of  hydrogen 
from  a  solution  of  a  sodium  salt  is  readily  understood.  Since 
the  voltage  required  for  the  discharge  of  the  sodium  ions  is 
much  greater  than  that  required  to  discharge  the  hydrogen 
ions  which  are  also  present,  the  latter  are  discharged;  and  the 
hydroxyl  ions  which  are  formed  from  the  water  as  the  hydrogen 
ions  are  discharged  impart  the  alkalinity  to  the  solution,  or  in 
other  words,  they  together  with  the  sodium  ions  form  sodium 
hydroxide. 

Since  oxygen  is  obtained  during  electrolysis  at  a  platinum 
anode  surrounded  by  a  solution  of  a  sulphate,  it  follows  that  the 
oxygen  ions  of  the  water  are  more  easily  discharged  than  the 
sulphate  ions  themselves;  and  the  hydrogen  ions  which  are 
formed  from  the  water  as  the  oxygen  ions  are  discharged  impart 
the  acidity  to  the  solution,  or  in  other  words,  they  together  wtih 
the  sulphate  ions  form  sulphuric  acid. 

The  Electro-Motive  Force  of  Battery  Cells. 

The  subject  of  electrolysis  has  not  been  presented  fully  unless 
the  electro-motive  force  of  the  product  formed  at  the  poles  has 
been  pointed  out,  and  since  this  electro-motive  force  when  con- 
sidered by  itself  presents  the  cell  as  a  galvanic  battery,  it  is  ad- 
visable to  consider  the  latter  subject  in  this  connection. 

In  the  treatment  of  this  topic  as  in  the  treatment  of  elee- 


88  University  of  Texas  Bulletin 

trolysis,  it  must  be  realized  that  the  fundamental  fact  is  the  utter 
independence  of  the  chemical  actions  which  take  place  or  tend 
to  take  place  at  the  two  poles.  Without  this  a  logical  presenta- 
tion of  the  facts  involved  becomes  practically  impossible  and  it 
is  on  this  account  that  the  methods  of  presentation  now  ordi- 
narily employed  are  comparatively  valueless,  if  not  actually 
harmful. 

For  the  following  experimental  demonstration,  secure  four 
small  porous  cups,  a  jar  with  strong  sodium  chloride  solution, 
and  a  sensitive  voltmeter  with  a  total  range  of  three  volts  or 
very  little  more.  Fit  the  cups  with  cork  or  rubber  stoppers, 
which  are  to  be  perforated  to  fit  the  electrode  rods  mentioned 
below.  With  one  porous  cup  make  a  chlorine  pole  by  using  a 
carbon  electrode  rod,  filling  the  cup  with  a  mixture  of  equal 
parts  of  concentrated  hydrochloric  acid  and  water,  and  then 
saturating  the  solution  with  chlorine  (preferably  by  electrolysis, 
otherwise  by  adding  a  little  potassium  permanganate).  For  the 
second  pole,  fill  the  cup  with  zinc  sulphate  solution,  and  use  a 
rod  of  zinc  for  the  electrode  rod.  For  the  third  pole,  use  a  plat- 
inum pole  (see  page  33) — or,  less  suitably,  a  carbon  rod,  and  fill 
the  cup  with  ferric  chloride  solution  to  which  has  been  added  a 
little  of  a  ferrous  salt  (FeSOJ.  For  the  fourth  pole  use  a 
copper  rod  and  copper  sulphate  solution. 

Put  the  copper  sulphate  pole  into  the  salt  solution  jar  and 
then  put  with  it  in  turn  each  one  of  the  other  three  poles  and 
measure  the  voltage  between  each'  of  them  and  the  copper 
sulphate  pole.  Now  plot  the  results  on  a  line  as  follows: 
mark  a  point  on  the  line  to  denote  the  voltage  of  the  copper- 
copper  sulphate  pole  and  refer  to  it  arbitraily  as  a  "zero 
voltage."  Since  the  zinc  sulphate  pole  is  the  negative  pole 
when  combined  into  a  cell  with  this  copper-copper  sulphate 
pole,,  and  since  the  combination  has  a  voltage  of  (about)  1.1 
volts,  then  if  we  consider  the  force  of  the  copper  pole  to  be 
zero  (arbitrarily),  it  follows  that  the  voltage  of  the  zinc  pole 
is  — 1.1  volts.  To  represent  this  on  our  plot  we  measure 
from  the  copper  pole  point  eleven  spaces  of  any  arbitrary 
length  to  the  left  arid  mark  this  point  (see  Fig.  11).  Then 
lay  off  the  voltage  of  the  chlorine  pole  (which  is  about  +1.0 
volt)  and  the  voltage  of  the  ferrous- ferric  salt  pole  (the  lat- 


Chemistry  in  High  Schools  89 

ter  will  be  about  +.4  to  +.5  volts.)  Measure  next  the  voltage 
of  all  other  combinations  of  any  two  of  these  poles  and  com- 
pare the  values  obtained  with  the  number  of  unit  lengths  be- 
tween them  shown  in  the  plot.  It  will  be  found  that,  allow- 
ing for  slight  inaccuracies  due  to  this  rough  procedure,  the 
numbers  will  agree.  This  shows  that  the  voltage  of  a  cell  is 
the  sum  of  the  two  independent  voltages  of  the  poles. 

The  primary  cause  of  the  action  of  a  pole  is  the  natural 
tendency  to  give  up  or  take  up  electrons  which  some  sub- 
stance present  at  the  pole  possesses;  e.  g.,  metals  and  hydrogen 
have  a  tendency  to  give  up  electrons  and  become  positively 
charged  ions;  while  non-metal  (oxygen,  chlorine,  bromine,  iodine) 
possess  a  tendency  to  take  up  electrons  and  become  negatively 
charged  ions. 

Such  tendencies  to  give  up  or  take  up  electrons  depend  also 
on  the  particular  resulting  substances  formed:  many  resulting 
substances  may  be  changed  back  simply  by  reversing  the  direc- 
tion of  the  electric  change  (i.  e.,  reversing  the  direction  of  the 
current),  and  such  substances  actually  exert  tendencies  which 
oppose  the  tendencies  of  the  original  substances. 

Hence  the  force  of  a  pole  depends  on  the  nature  of  the  orig- 
inal substance  and  on  the  particular  kind  of  resulting  substance 
formed  during  its  action.  Furthermore,  the  force-  depends  on 
the  concentrations  of  the  original  and  of  the  resulting  substances  : 
both  the  forward  and  the  reverse  tendencies  to  change  increase 
somewhat  with  the  amounts,  per  cc.,  of  the  original  and  of  the  re- 
sulting substances  respectively.  Hence,  in  recording  measure- 
ments of  the  electromotive  forces  of  poles,  we  must  state  the  ex- 
act concentrations  of  the  original  and  of  the  resulting  substances 
in  the  poles  when  the  measurements  are  made.  Note  how  this  is 
done  in  the  table  on  page  110. 

These  pole-changes  may  be  expressed  by  equations.  Thus 
for  copper  and  zinc,  which  are  used  in  the  demonstrations 
above,  the  equations  are  : 

Cu°—  2(—  )=Cu** 
Zn°—  2—  =Zn**. 


The  Cu  and  Zn  on  the  left  side  of  the  equation  are  marked  with 
a  zero  to  denote  the  fact  that  they  are  elements,  i.  e.  they  have 


90  University  of  Texas  Bulletin 

no  ionic  charges.  An  electron  by  itself  is  represented  by  (  —  ), 
and  the  expression  —2  (  —  )  denotes  that  two  electrons  are  given 
up  by  one  atom  of  copper  or  of  zinc. 

For  the  other  two  substances,  the   expressions  of  the   pole 
changes  are  — 


Fe***+l(—  )=Fe** 

by  which  is  meant  that  these  substances  take  up  one  electron 
per  atom  and  become  chlorine  ion  and  ferrous  ion  respectively. 

But  although  a  particular  "pole"  may  have  a  tendency  to  give 
up  electrons,  it  cannot  actually  do  so  unless  it  is  connected  with 
another  pole  which  will  take  up  electrons.  When  the  "copper- 
copper  sulphate"  cup  is  placed  in  the  connecting  salt  trough, 
together  with  the  chlorine  cup,  and  the  poles  are  connected  by  a 
wire,  then  the  copper  actually  changes  to  Cu**  ions  because  the 
electrons  given  up  by  the  copper  are  "transferred"  in  a  sense 
through  the  wire  connection  to  the  chlorine  pole  and  are  there 
taken  up  by  neutral  chlorine,  which  becomes  Cl'  ions. 

In  this  particular  combination  both  elements  change  to  ions 
when  the  current  flows.  But  when  a  "copper-copper  sulphate" 
and  a  "zinc-zinc  sulphate"  pole  are  combined  into  a  cell,  then 
only  one  of  these  can  change  from  metal  to  ions,  i.  e.,  only  one 
metal  can  give  up  electrons,  and  the  other  takes  up  electrons 
and  changes  in  the  reverse  manner,  as  represented  by  this  ex- 
pression — 

Cu**+2(—  )=Cu° 

The  direction  in  which  a  pole  actually  changes  when  it  is  com- 
bined with  another  pole  to  form  a  cell  depends  upon  the  relation 
of  the  tendencies  of  the  two  poles.  This  relation  has  been  ascer- 
tained for  all  poles  by  ascertaining  the  relations  of  all  other  poles 
to  a  common  *  '  reference  "  or  "  zero  '  '  pole  :  since  the  tendency  of 
a  single  pole  is  independent  of  the  other  pole  with  which  it  is 
combined,  the  relation  between  this  reference  pole  and  all  other 
poles  gives  also  the  mutual  relations  between  these  other  poles. 
This  procedure  was  illustrated  in  the  demonstration  above.  All 
the  data  and  further  information  needed  in  this  connection  is 


Note. — An   asterisk    designates    positive   electric    charges;    an    apos- 
trophe, negative  charges. 


Chemistry  in  High  Schools  91 

given  in  the  "Table  of  Electromotive  Forces  of  Battery  Poles," 
pag'e  109,  which  see. 

Further  general  consideration  of  the  galvanic  cell  need  not 
be  given  here,  but  will  be  given  in  connection  with  the  subject 
of  oxidation  and  reduction  (which  see).  It  remains  only  to 
point  out  the  connection  between  battery  cells  and  electrolytic 
cells. 

The  substances  produced  by  electrolysis  (hydrogen  from 
acids  or  water,  copper  from  copper  salts,  chlorine  from  chlo- 
rides, etc.)  naturally  exert  a  tendency  to  regain  the  ionic  state, 
thus  each  pole  acts  as  the  pole  of  a  battery  with  an  electromo- 
tive force  opposite  to  the  applied  force.  This  is  the  electromo- 
tive force  of  polarization.  It  is  absent  before  electrolysis  be- 
gins and  hence  at  the  beginning  any  applied  force,  however 
small,  will  produce  a  current;  but  as  soon  as  products  of  the 
electrode  discharges  are  present,  their  electromotive  force  is 
exerted,  and  in  order  that  electrolysis  may  continue,  the  ap- 
plied force  must  be  larger  than  this  opposing  force. 

The  Action  of  General  Reagents  Upon  Solutions  of  Salts* 

The  action  of  reagants,  the  results  of  which  depend  only  on 
our  general  knowledge  of  solubility  and  ionic  dissociation,  has 
already  been  illustrated  above.  Many  other  reagents,  however, 
present  special  conditions  of  ionic  dissociation  which  require 
separate  consideration.  Of  the  reagents  which  present  special 
conditions,  only  those  commonly  used  will  be  considered.  It 
will  be  found  that  the  special  properties  of  the  latter  are  also 
essential  parts  of  chemical  information. 

1.    Sodium  (or  Potassium)  Hydroxide  as  a  Reagent. 

Experiment.  Secure  solutions  of  water  soluble  salts  of  the 
following  cations:  Cu,  Ag,  Zn,  Cd,  Hg  (ous),  Hg  (ic),  Pb, 
Fe  (ous),  Fe  (ic),  Ni,  Al,  Mg,  Ca. 

To  a  few  cubic  centimeters  of  each  of  these  solutions  in  a 
test-tube  add  a  few  drops  of  sodium  hydroxide  solution,  shake 
in  order  to  mix  thoroughly,  observe  the  effect,  add  a  few  drops 
more  of  the  reagent,  and  so  continue  until  the  reagent  has  been 

*Read  pages  49  and  50  in  this  connection. 


92  University  of  Texas  Bulletin 

added  in  a  relatively  large  amount,  say  about  twice  as  much 
reagent  by  volume  as  of  salt  solution,  if  the  two  solutions  are 
of  approximately  equivalent  concentrations.  Compare  the  re- 
sults with  the  statements  in  the  table  below. 

General  Facts.  By  strict  metathetical  reaction  the  hydrox- 
ides should  be  obtained  in  the  mixtures  below.  However,  in 
many  cases  the  substances  finally  obtained  are  not  the  hydrox- 
ides of  the  metals  but  substances  derived  from  them  through 
one  or  both  of  the  two  following  changes: 

(a)  Dehydration, — complete  (Hg(OH)2  to  HgO)    or  partial 
(Cn(OH)2toCu802  (OH)2). 

(b)  Dissolution  of  the  precipitated  hydroxide  by  excess    of 
the  reagent,  thus  showing  that  the  precipitated  hydroxide  func- 
tionates as  an  acid,  e.  g.  Zn(OH)2  dissolves  in  excess  of  NaOH 
solution  as  per  equation: 

H2Zn02+NaOH= Na2ZnO,+2H20. 

The  formula  for  zinc  hydroxide  is  thus  written  to  suggest  its 
functionating  as  an  acid. 

Table  showing  Results  of  Action  of  NaOH  (or  KOH)   Solu- 
tions upon  '  *  Water  Soluble ' '  Salts  of  the  Following  Metals : 
Ba — Ba(OH)2  is  precipitated  only    from    concentrated  solu- 
tions because  it  is  soluble  in  20  parts  of  water — white. 
Sr— Ppt.  Sr(OH)2  sol.  in  60  parts  of  H20— white— not  pre- 
cipitated from  dilute  solutions. 

Ca— Ppt.  Ca(OH)2  sol.  in  700  parts  H20— white— not  pre- 
cipitated from  very  dilute  solutions. 
Mg— Ppt.  Mg(OH)2  sol.  in  6000  parts  H20— white. 

Al — Ppt.  A1(OH)3  white,  sol.   in  excess  of  reagent,  giving 

NaA102. 

Zn— Ppt.  Zn(OH)2  white,  sol.  in  excess— Na2Zn02. 
Pb— Ppt.  Pb(OH)2  white,  sol.  in  excess— Na2Pb02. 
Ferrous — Fe(OH)2  white  ppt.,  darkens  on  exposure  to  air 

(oxidizes). 

Ferric — Fe(OII)3  reddish  brown,  flocculent  ppt. 
Mn — Ppt.  Mn ( OH )2— "flesh"  colored,  darkens  on  exposure  to 

air. 
Ni— Ppt.  Ni(OH)2— pale  green. 


Chemistry  in  High  Schools  93 

Cu — in  cold  solution,  Cu(OH)2 — bluish  white  ppt.,  soluble  in 
large  excess  of  reagent;  in  hot  solution,  CuO — black 
ppt. 

Cd— Cd(OH)2,  white  ppt. 
Bi— Bi(OH)3,  white  ppt. 
Ag — Ppt.  Ag20 — greyish  brown. 
Hg(— ous)— Ppt.  Hg20— black. 

Hg  (ic) — Ppt.  HgO — yellow — in  order  to  avoid  the  forma- 
tion of  different  colored  basic  salts,  the  Hg  salt  solu- 
tion must  be  poured  into  the  reagent. 

Exercise  (a).  In  what  way  can  it  be  readily  ascertained 
whether  or  not  a  substance  has  been  completely  precipitated, 
say  Fe(OH)3  by  NaOH?  Hence  would  sodium  hydroxide 
be  employed  as  a  precipitant  for  aluminium  if  it  be  required 
that  precipitation  be  complete?  From  the  metals  given  in  the 
table  above  select  those  for  which  sodium  hydroxide  may  thus 
be  used  as  a  precipitant. 

(b)  Since  it  is  easy  to  convert  a  hydroxide  completely  to 
any  salt  by  treatment  with  the  necessary  acid,  and  there  is  no 
troublesome    ( ?)   by-product  formed,  it  is  plain  why  the  pre- 
cipitation of  metals  in  the  form  of  hydroxides  is  very  desirable. 
By  means  of  such  an  intermediate  step  many  metals  may  be 
readily  changed  from  one  salt  to  another — a  change  that  may 
not  be  possible  in    one    step    otherwise.     Give  directions    for 
changing  the  magnesium  in  magnesium  sulphate  to  magnesium 
chloride;  also  for  changing  copper  in  copper  nitrate  to  copper 
chloride. 

(c)  Given  a  solution  containing  aluminium  and  ferric  salts. 
State  how  these  metals  may  be  obtained  separately  in  the  form 
of  any  compound.     Similarly,  how  may  zinc  and  cadmium  be 
separated  ? 

2.     Ammonia  as  a  Reagent. 

Preliminary  Considerations.  Since  a  solution  of  ammonia 
contains  OH  ions  we  expect  to  find  that  it  reacts  just  as  sodium 
hydroxide  does  in  the  preceding  exercise;  that  is,  as  a  reagent 
to  precipitate  metal  hydroxides.  However,  it  differs  from  so- 
dium hydroxide  in  being  a  weak  base,  and  hence  it  has  no  effect 


94  University  of  Texas  Bulletin 

on  solutions  of  salts  of  the  strong  bases  (which  are  these?). 
With  reference  to  the  other  bases,  the  following  holds.  Am- 
monia precipitates  the  hydroxides  of  the  trivalent  metals  com- 
pletely under  all  conditions,  but  it  does  not  precipitate  these 
of  the  other  weak-basic  cations  if  enough  of  an  ammonium  salt 
(i.  e.}  many  NH*  ions)  is  present  (exceptions — lead  and  mer- 
cury, which  with  ammonia  always  form  insoluble,  complex  am- 
monium compounds).  This  influence  of  the  NH*  ion  is  ex- 
erted as  follows:  since  ammonia  is  very  slightly  ionized,  the 
product  (NH4*)X(OH'),  which  holds  an  equilibrium  with  the 
undissociated  NH4OH,  must  remain  practically  constant;  hence 
when  (NH4*)  is  increased  by  the  addition  of  an  ammonium 
salt  (e.  g.  HN4C1)  which  is  largely  dissociated,  (OH')  must  de- 
crease, or  in  other  words,  ammonia  is  less  dissociated  in  the 
presence  of  an  ammonium  salt  than  in  the,  absence  of  the  latter. 
The  concentration  of  the  OH  ion  in  such  a  mixture  is  so  small 
that  the  product  obtained  by  multiplying  this  OH '  concentration 
with  the  concentration  of  any  bivalent  metal  ion  that  may  be 
added  ( [M*]  X  [OH] ')  will  be  less  than  the  "ion-product"  that 
a  resulting  precipitate  itself  could  produce.  The  formation  of 
a  precipitate  does  not  take  place  because  thereby  the  ion-product 
would  be  increased,  and  reactions  take  place  only  when  an  ion- 
product  is  decreased.  But  the  ion-products  of  the  tri-valent- 
metal-hydroxides  are  smaller  than  those  of  the  bivalent-metal- 
hydroxides,  and  whenever  a  tri-valent-metal-ion  is  introduced 
into  a  solution  containing  any  OH'  ions,  the  product  [M]  X  [OH] 
is  always  greater  than  the  ion-product  of  the  precipitate, — hence 
the  precipitate  is  formed  because  thereby  the  product  of  these 
ions  in  this  solution  is  reduced. 

To  demonstrate  this  effect,  add  some  ammonia  to  one  portion 
of  magnesium  chloride  solution,  and  to  another  portion  add 
some  ammonium  chloride  solution  and  then  ammonia. 

Exercise.  By  the  use  of  ammonia,  separate  bismuth  from  a 
solution  containing  bismuth  and  copper  salts;  Al  from  a  solu- 
tion containing  Al  and  Ni  salts;  Fe  (ic)  from  a  solution  con- 
taining ferric  and  Mg  Salts. 

Give  directions  for  changing  the  aluminium  in  potash  alum 
completely  to  aluminium  chloride. 


Chemistry  in  High  Schools  95 

3.     Soluble  Sulphides  as  Reagents. 

Note.  Hydrogen  sulphide  is  poisonous,  hence  the  generators 
of  this  gas  should  be  used  either  outside  of  the  building  or  in  well 
drawing  hoods. 

Preliminary  Considerations.  Since  all  sulphides  except  those 
of  the  alkali  and  alkaline  earth  metals  (Na,  K,  "NH4,"  Ca, 
Sr,  Ba,  Mg)  are  insoluble,  it  is  to  be  expected  that  a  precipi- 
tate of  the  corresponding  sulphide  will  be  obtained  whenever 
a  soluble  sulphide  is  added  to  a  solution  of  a  salt  of  any  of  the 
other  metals.  And  such  is  the  case  except  when  hydrogen 
sulphide  is  used.  Judging  from  its  properties,  this  substance 
appears  to  be  an  exceedingly  weak  acid — very  slightly  disso- 
ciated— and  its  ion  product  (H*)X(S")  is  very  small.  A 
great  increase  of  H*  ions,  through  the  addition  of  a  strong  acid, 
lessens  its  S"  concentration  greatly  for  the  same  reason  that 
an  increase  of  NH4  ion  concentration  decreases  the  OH'  con- 
centration in  ammonia.  Hence  the  following  general  fact  con- 
cerning the  effect  of  hydrogen  sulphide  as  a  regeant:- 

Even  in  the  presence  of  a  moderate  concentration  of  hydro- 
gen ions  (a  strong  acid),  hydrogen  sulphide  precipitates  com- 
pletely the  sulphides  of  some  metals,  among  them  Ag,  Hg,  Pb, 
Bi.  and  Cd,  which  for  convenience  may  be  called  the  hydrogen 
sulphide  group;  and  only  in  the  absence  of  hydrogen  ions  (ab- 
sence of  acid)  does  it  precipitate  completely  the  sulphides  of 
other  metals,  among  which  may  be  mentioned  Fe,  Zn,  Ni,  Mn, 
the  ammonium  sulphide  group. 

Demonstration.  Put  10  to  20  cc.  of  dilute  copper  sulphate 
solution  and  an  equal  amount  of  zinc  sulphate  solu- 
tion in  a  small  flask,  add  10  to  20  drops  of  dilute  HC1,  heat 
to  boiling,  treat  with  H2S  in  excess  and  filter.  What  is  the  sub- 
stance on  the  filter  paper?  The  reaction  that  has  taken  place 
is  metathetical — write  the  equation.  What  is  the  by-product? 
Evidently  the  concentration  of  the  hydrogen  ion  has  been  in- 
creased during  the  progress  of  the  reaction.  Since  with  exces- 
sive concentration  of  hydrogen  ion,  hydrogen  sulphide  is  un- 
able to  precipitate  sulphides  of  this  group  even  (?),  and  since 
it  is  possible  that  in  this  experiment  the  concentration  of  the 
acid  has  become  excessive,  the  last  portion  of  copper  may  not 


96  University  of  Texas  Bulletin 

be  precipitable  under  the  conditions.  Hence  a  small  part  of 
the  solution  must  be  diluted  largely  by  adding  an  equal  volume 
or  more  of  water,  or  the  acid  may  be  partially  neutralized  by 
the  cautious  addition  of  a  base.  Then  it  should  be  heated  again 
and  treated  with  hydrogen  sulphide.  If  necessary,  treat  the 
main  portion  of  the  solution  in  this  way  and  repeat  this  pro- 
cedure until  precipitation  is  complete. 

Before  proceeding  to  precipitate  the  zinc  sulphide,  it  is  de- 
sirable to  remove  the  remnant  of  hydrogen  sulphide  which  re- 
mains dissolved  in  the  liquid,  since  otherwise  it  starts  precip- 
itation :as  soon  as  the  acid  is  neutralized  by  ammonia  or  any 
other  base.  To  remove  this  gas,  boil  the  liquid  well  for  two  or 
three  minutes. 

Then  add  ammonia  to  the  clear  (and  odorless)  solution  until 
it  is  plainly  alkaline.  If  enough  ammonium  salt  is  present 
(from  what  source?),  then  no  precipitate  will  be  formed.  Next, 
treat  the  solution  with  hydrogen  sulphide  again.  A  white  pre- 
cipitate (ZnS)  will  be  formed  (a  trace  of  iron  compounds  in- 
troduced by  the  hydrogen  sulphide  may  impart  a  "dirty"  color 
to  the  precipitate).  Filter  and  wash  the  precipitate. 

The  ammonia  added  above  performs  two  functions:  first,  it 
neutralizes  the  free  acid  present,  and  second,  it  forms  ammo- 
nium sulphide  with  the  hydrogen  sulphide.  Write  the  meta- 
thetical  reaction  of  the  action  of  ammonium  sulphide  with  the  zinc 
salt. 

Transfer  the  CuS  to  a  dish,  add  a  little  dilute  HN03,  and 
warm  the  mixture.  A  solution  of  Cu  (N03)2  will  be  obtained 
by  complex  reaction.  Note  the  free  sulphur  formed. 

Drip  dilute  HC1  slowly  upon  the  ZnS  on  its  filter  paper  until 
all  has  been  dissolved  and  collected  in  a  beaker  placed  below. 
The  reaction  is  metathetical  ( ? ) .  Note  the  evolution  of  H2S. 

What  is  the  object  of  this  whole  experiment? 

Reactivities  of  Sulphides. 

The  reagents  under  (b)  and  (c)  below  will  also  react  upon 
the  sulphides  in  the  groups  above  their  own;  but  the  reagents 
of  (a)  and  (b)  do  not  react  upon  the  sulphides  in  the  groups 


Chemistry  in  High  Schools  97 

below  them.     In  all  cases  the  metals  dissolve  because  they  are 
changed  to  water  soluble  salts. 

(a)  Sulphides  which  react  metathetically  with  dilute  HC1 
or  dilute  H2S04  :— 

ZnS,  FeS,  MnS,  CdS. 
CdS  requires  a  stronger  "dilute"  HC1  than  the  others. 

(b)  Sulphides  which  react  with  dilute  HN03— action  com- 
plex, resulting  in  free  sulphur  and  nitrates  of  metals:— 

Ag2S,  PbS,  CuS,  Bi2S3. 

(c)  Sulphides  which  react  with  aqua  regia  only  (aqua  regia 
is  essentially  a  concentrated  solution  of    free  chlorine    which 
acts  to  produce  free  sulphur  and  chlorides  of  the  metals)  : — 

NiS,  CoS,  HgS. 

Colors  of  Sulphides. 

The  colors  of  sulphides  are  a  valuable  means  of  identifying 
the  metals.  By  proper  means  (?)  prepare  small  portions  of  the 
colored  sulphides.  They  have  the  following  colors: — 

FeS,  NiS,  Ag2S,  HgS,  PbS,  Bi2S3— dull  black. 
CuS — brownish  black. 
ZnS— White  (when  pure!). 
CdS— yellow. 

MnS — pink  or  flesh  color. 

Note: — during  precipitation  HgS  frequently  exhibits  several 
other  colors — black,  yellow,  red — but  with  excess  of  H2S  it 
finally  becomes  black. 

Exercise.  For  how  many  metals  may  soluble  sulphides  be 
used  as  precipitation  reagents?  Into  how  many  classes  may 
metals  be  separated  by  means  of  soluble  sulphides?  The  an- 
swers to  these  two  questions  will  indicate  why  soluble  sulphides 
are  the  most  valuble  general  reagents  known. 

Precipitate  separately  as  sulphides  the  metals  from  a  solution 
containing  any  one  of  the  following  pairs  of  metals — copper  and 
zinc,  cadmium  and  nickel,  bismuth  and  manganese.  Continue  the 
treatment  for  the  precipitation  of  the  first  metal  until  the  second 
sulphide  can  be  obtained  pure — as  shown  by  its  color.  Wash 
the  copper,  cadmium,  or  bismuth  sulphide  with  distilled  water 
while  it  is  on  the  filter  paper  (to  remove  remnants  of  the  salt  of 


98  University  of  Texas  Bulletin 

the  second  metal),  and  convert  it  to  the  nitrate.  Convert  the 
zinc,  nickel,  or  manganese  to  the  chloride. 

List  of  Useful  Special  Properties  and  Reactions  of  Metals. 

These  properties  and  reactions  are  only  briefly  indicated  here. 
Consult  a  text  book  for  further  information.  These  properties 
and  reactions  need  not  be  definitely  remembered,  since  they  may 
be  looked  up  when  needed.  The  student  should  make  simple 
trials  to  acquaint  himself  experimentally  with  these  facts. 

1.  AgCl  is  soluble  in  ammonia,  from  which  solution  AgCl 
may  be  reobtained  by  neutralizing  the  ammonia  with  an  acid 
(HNO,-). 

2.  PbCl2  is  very  soluble  in  hot  water,  though  not  in  cold 
water. 

3.  HgCl  forms  a  black  compound  with  ammonia,  for  which 
the  formula  and  reaction  need  not  be  learned. 

4.  HgCl2  is  reduced  to  HgCl  or  Hg  by  SnC'l2  solution,  the 
latter  becoming  SnCl4. 

5.  Bi  salt  solutions  hydrolyze  when  the  concentration  of  free 
acid  (H*  ion!)  in  the  solution  falls  below  :a  certain  limit.    "Hy- 
drolysis "is  a  metathetical  reaction  between  water  and  a  salt 
which  produces  the  free  acid  and  the  free  base  (or  a  basic  salt), 
e.  g.  BiCl3+H20=BiOCl+2HCl. 

A1,S3+6H20=2A1(OH)3+3H2S. 

All  salts  of  weak  acids  or  of  weak  bases  are  hydrolyzod,  though 
some  only  so  slightly  that  the  effect  can  not  be  noticed  except 
by  some  delicate  means  such  as  the  effect  upon  litmus.  For 
demonstration,  test  solutions  of  the  following  normal  salts  with 
litmus : 

Sodium  carbonate. 

Sodium  acetate. 

Copper  sulphate. 

Zinc  chloride. 


Chemistry  in  High  Schools  99 

6.  Note  that  the  following  salts  and  their  solutions  are  col- 
ored : — 

Copper  salts — blue  or  green. 
Nickel  salts — blue  or  green. 
Ferrous  salts — pale  green. 
Ferric  salts — reddish  yellow. 
Manganous  salts — pale  amethyst. 

7.  Compounds  of  the  following  metals  will  color  the  Bunsen 
flame.     To  try  this  use  a  clean  platinum  wire,  dip  it  into  solu- 
tions of  these  metals  and  hold  the  drop  of  the  solution  in  the 
flame : — 

Bright  red— Sr. 
Brick  red — Ca. 
Yellow— Na. 
Yellowish  green — Ba. 
Green  to  blue— Cu. 
Blue,  pale— Pb. 
'  Violet— K. 

8.  Ammonia  in  compounds  is  revealed  by  treating  them  with 
a  strong  base  (e.  g.  NaOH  solution),  warming  the  mixture,  and 
noting  the  odor. 

9.  Sodium  hydroxide  cannot  be  used  as  a  precipitating  rea- 
gent in  the  presence  of  ammonium  salts  because  it  reacts  with 
the  latter.     Ammonium  salts  may  be  removed  by  evaporating 
the  solution  to  dryness  and  then  heating  the  dish  and  contents 
to  low  redness  until  fumes  cease  to  be  given  oft*. 

Chemical  Problems. 

The  following  problems  are  to  be  solved  by  means  of  the  fore- 
going facts: 

1.  Students  should  be  given  solutions  of  water  soluble  salts, 
each  solution  should  contain  only  one  metal,  and  the  student 
should  ascertain  what  the  metal  is.  Salts  of  the  following  inetals 
may  be  given — copper,  silver,  bismuth,  lead,  mercury  (both 
valences),  cadmium,  iron  (ferric  only)  manganese,  nickel,  zinc, 
calcium,  strontium,  barium,  magnesium,  sodium,  potassium,  am- 
monium. Twelve  to  fifteen  solutions  should  thus  be  worked  out 
by  every  student. 


100  University  of  Texas  Bulletin 

In  trying  to  find  the  metal,  the  student  should  note  the  color 
of  the  solution;  he  should  ascertain  if  it  would  color  the  flame 
of  the  Bunsen  burner;  and  on  very  small  portions  of  the  solu- 
tion he  should  try  the  effect  of  reagents  in  the  order  given  be- 
low. 

(a)  Add  dilute  hydrochloric  acid.     If  a  precipitate  is  ob- 
tained, then  special  tests  1  to  3  should  be  tried  on  the  ppt.  after 
it  has  been  filtered  off  and  washed. 

(b)  Add  dilute  sulphuric  acid. 

(c)  Acidify  moderately  with  either  HOI  or  H2S04  (which- 
ever produces  no  precipitate),  and  then  treat  wtih  hydrogen 
sulphide  (see  "g"  below). 

(d)  Add   ammonium   chloride   and   ammonia.     Ammonium 
chloride  will  produce  a  ppt.  if  HC1  did,  but  such  a  ppt.  should 
be  removed  by  filtration  before  ammonia  is  added. 

(e)  Irrespective  of  the  presence  or  absence  of  any  ppt.  pro- 
duced by  ammonia,  treat  the  resulting  mixture  from  (d)  with 
hydrogen  sulphide  (see  "g"  below). 

(f )  Add  sodium  hydroxide. 

(g)  If  a  black  sulphide  has  been  obtained,  then  to  decide 
which  metal  sulphide  it  is,  try  special  tests  4  and  5  above,  and 
also  ascertain  the  reactivity  of  the  sulphide  with  acids  after  it 
has  been  filtered  off  and  washed. 

2.  Prepare  KNO3  by  the  commercial  method,  from  NaN03 
and  KC1.     (See  Smith,  Art.  127.) 

3.  Prepare  NaOH  by  the  commercial  method,  from  Na2C03 
and  Ca(OH)2.     (See  Smith,  Art.  126.) 

4.  Prepare  pure  sodium  chloride  by  precipitation  with  HC1. 
(See  Smith,  Art.  132.) 

Text-Book  Reading. 

Parallel  with  this  laboratory  work  on  the  metals  some  of  the 
usual  text-book  reading  found  under  the  various  metals  should 
be  given.  However,  it  should  be  more  or  less  confined  to  the 
commerically  imporant  facts  and  compounds,  such  as  the  com- 
mercial sources,  and  the  methods  of  preparation,  from  these 
sources,  of  the  commercially  important  products. 

The  choice  of  what  is  commercially  important  varies  some- 


Chemistry  in  High  Schools  101 

what  with  the  locality.  In  an  agricultural  state  such  as  Texas 
the  source  of  potassium  salts  and  the  composition  of  fertilizers 
is  of  vastly  greater  importance  than  the  source  of  copper,  and 
the  methods  of  its  extraction  from  its  ores;  while  in  a  mining 
state  such  as  Arizona  just  the  reverse  holds  good.  The  empha- 
sis in  the  informational  reading  should  be  laid  accordingly. 

Chemical  Changes  Involving  Oxidation  and  Reduction. 

lonisation  and  Valence.  In  contradistinction  to  the  changes 
studied  thus  far  (metathetical  changes  and  hydration)  in  which 
the  valence  of  all  ions  (or  constituent  parts  of  compounds)  re- 
mained constant,  the  changes  now  to  be  studied  specially .  are 
those  involving  changes  of  valences.  As  has  been  shown,  valence 
means  the  number  of  electric  charges  on  an  ion  (or  that  would 
be  on  any  particular  part  of  an  acid,  base,  or  salt  after  it  had 
been  changed  to  an  ion).  Thus  the  valence  of  the  N03 
ion  is  1  because  in  the  ionization  of  any  one  of  its  com- 
pounds— e.  g.  NaN03  or  HNO3,  the  Na  or  H  gives  one  negative 
ionic  charge  (electron)  to  the  N03. 

So  far  the  attention  has  not  been  directed  to  the  complete 
ionisation  of  such  complex  compounds  as  HN03,  NH4C1,  CuS04, 
etc.,  which  would  yield  each  element  of  a  compound  in  the  form 
of  a  separate  ion,  and  this  must  now  be  taken  up.  Thus  the  pri- 
mary ionisation  of  NH4C1  yields  NH4*  and  Cl',  but  complete 
ionisation  into  the  elemental  parts  requires  the  further  ionisa- 
tion of  NH4*.  Since  4H*  result  from  this  ionization,  and  thus 
3  new  (-]-)  charges  appear,  it  follows  that  3  ( — )  have  been 
given  up  by  the  H's  and  left  upon  the  N  ion  (written  N3'  or 
N'").  The  whole  compound  in  the  form  of  ions  may  be  ex- 
pressed thus  (4H*,  N3',  Cl').  In  the  same  way  the  complete 
ionisation  of  H.,SO4  requires,  after  the  primary  ionisation  into 
2H*  and  S04",  the  further  ionisation  of  S04".  Since  40" 
would  result  from  this  secondary  ionisation,  and  hence  6  new 
( — )  charges  appear,  then  the  6  (  +  )  produced  simultaneously 

Note. — An  asterisk  designates  positive  electric  charges;  an  apos- 
trophe, negative  charges. 


102  University  of  Texas  Bulletin 

must  reside  on  the  S  ion  (written  S6*  or  S******).'  The  whole 
may  be  written  2H*,  S6*,  40". 

It  is  a  general  fact  that  in  aqueous  solutions  hydrogen  and 
metals  become  cations  while  0  (or  OH),  the  halogens  (F,  Cl, 
Br,  I)  and  the  cyanogen  radical  (ON)  all  become  anions. 

It  has  been  shown  above  that  in  electrolytic  and  battery  cells, 
during  action,  the  substances  at  one  pole  undergo  one  kind  of  a 
valence  change  while  the  substances  present  at  the  other  pole 
undergo  the  opposite  kind  of  a  valence  change. 

The  proportion  of  the  substances  changing  valences  simul- 
taneously at  the  two  poles  depends  merely  upon  the  fact  that 
the  number  of  electrons  simultaneously  transferred  "at"  the 
two.  poles  are  equal  (but  they  are  transferred  in  opposite  senses 
at  the  two  poles).  Thus  if  the  two  "pole  changes"  are 


then  the  proportion  in'  which  the  two  substances  change  simul- 
taneously is  Zn  :2C1. 

When  the  results  produced  upon  a  substance  by  these  changes 
in  valence  are  compared  with  the  results  produced  upon  it  by 
oxidizing  (or  reducing)  agents,  it  is  found  that  an  increase  of 
positive  ionic  charges  (or  decrease  of  negative)  produces  the 
same  result  as  oxidation,  and  the  reverse  electric  change  pro- 
duces the  same  result  as  reduction.  This  has  been  found  to  be 
always  true.  For  illustration,  consider  the  production  of  chlo- 
rine from  HC1.  Hence  the  following  simple  and  perfectly  gen- 
eral definition:  —  oxidation  is  the  increase  of  positive  charges 
or  valences  of  an  element  or  radical  (or  the  decrease  of  negative 
charges).  Reduction  is  the  reverse  change. 

Exercise. 

Ascertain  whether  the  elements  italicized  when  changed  from 
the  first  to  the  second  form  undergo  oxidation  or  reduction. 
Express  the  amount  of  change  in  numbers  of  ionic  charges  per 
atom  of  the  changed  element. 


Chemistry  in  High  Schools  103 

First  Form.  Second  Form. 

(a)  KCl  HC7 

(b)  Chlorine  HCl 
(e)  ZnS04                                                          ZnCl2 
(d).  Zinc                                                            ZnC\2 

(e)  K2S04  KCl 

(f)  UNO,  #H4OH 

(g)  KMnO,  MnS04 

(h)  \FeS04  FeCl3 

(i)  K2CrO4  CrCl, 

In  the  light  of  this  definition  of  oxidation  and  reduction,  it  is 
seen  that  in  every  electrolytic  cell  and  every  battery  cell,  oxida- 
tion takes  place  at  one  pole,  and  reduction  at  the  other. 

Study  next  the  "Table  of  Electromotive  Forces  of  Battery 
Poles,"  page  109. 

If  the  "valence-changing"  substances  of  the  two  poles  of  a 
battery  cell  are  put  in  direct  contact,  (i  e.  mixed  together)  they 
will  undergo  the  same  changes  without  the  use  of  the  metallic 
poles  and  their  connecting  wires.  Here  evidently  the  transfer 
of  the  electrons  is  direct  from  one  valence-changing  substance 
to  the  other.  This  is  easily  shown  by  the  following  test-tube 
trials  with  some  of  the  same  substances  used  in  the  battery  cells 
shown  before : — 

(a)  Put  granulated  zinc  into  some  copper  sulphate  solution, 
and  shake  the  mixture  at  intervals  until  the  solution  is 
colorless.    Then  test  solution  .with  H2S  for  zinc  ion.    Con- 
clusion ? 

(b)  In  place  of  chlorine  in  a  chloride  solution  it  is  better  to 
use  iodine  dissolved  in  KI  solution   (or  bromine  water). 
Treat  this  with  zinc  until  the  free  iodine   (or  bromine) 
has  disappeared.     Then   test  the  solution  for  zinc  ion. 
Conclusion  ? 

(c)  Treat  a  ferric  chloride  solution  with  zinc  until  the  red- 
dish brown  color  of  the  ferric  ion  has  disappeared.     Test 
with  NH4C1  and  NH4OH  to  ascertain  if  the  change    is 
complete. 


104  University  of  Texas  Bulletin 

k     The  three  equations  for  these  reactions  are: — 

(a)  Zn°  +Cu2'S04:=ZnS04-f  Cu 

to  2»      to  0 

(b)  Zn°  +21°  =ZnI2. 

to  2*          to  1' 

(c)  Zn°  -f-2Fe3*Cl3=ZnCl2+2FeCl2. 

to  2*  to  2* 

The  numbers  of  electric  charges  on  the  valence  changing  sub- 
stances are  written  as  shown  in  order  to  show  at  a  glance 
which  substances  are  oxidized  and  which  are  reduced.  Point 
out  which  are  oxidized, — which  reduced. 

The  proportion  between  the  valence-changing  substances  in  a 
reaction  is  determined  by  making  the  number  of  electrons  given 
up  by  one  substance  equal  to  the  number  of  electrons  taken  up 
by  the  other  substance.  Thus  in  (b)  above,  one  Zn  gives  up 
2( — )  while  one  I  takes  up  only  1( — ) ;  hence  their  ratio  in  the 
reaction  is  IZn  to  21.  Another  way  of  stating  the  fact  is  to  say 
that  the  amount  of  oxidation  in  a  reaction  is  equal  to  the  amount 
of  reduction. 

Exercise : 

Make  test  tube  trials  of  the  following  substances : — 

1.  Treat  ferric  chloride  solution  with  excess  of  hydrogen  sul- 
phide, and  test  with  ammonium  hydroxide. 

2.  Add  a  slight  excess  of  bromine  water  to  a  ferrous  salt  solu- 
tion and  test  with  NH4OH. . 

3.  Treat  dilute  bromine  water  with  hydrogen  sulphide. 

4  Put  a  rod  of  zinc  into  a  concentrated  solution  of  stannous 
chloride. 

5.  Put  a  piece  of  copper  into  some  mercuric  chloride  or  nitrate 
solution. 

Write  the  equations  for  these  reactions  as  in  the  illustration 
above. 

The  foregoing  reactions  are  evidently  quite  simple,  yet  they 
present  all  the  principles  involved,  and  other  reactions  which 
appear  to  be  more  complex  really  involve  no  new  facts.  As  a 


Chemistry  in  High  Schools  105 

rule  they  differ  only  by  involving  some  additional  metathetical 
actions.  This  is  well  illustrated  by  the  oxidizing  actions  of  HNO, 
which  will  now  be  discussed. 

Nitric  acid  and  its  Reduction  Products.  The  following  should 
be  among  the  experiments  shown :  — 

1.  The  preparation  of  HN03  by  distillation  from  NaN03  and 
concentrated  H2S04. 

2.  The  ease  with  which  HN03  gives  up  oxygen  is  strikingly 
illustrated  by  dropping  a  glowing  piece  of  charcoal  into 
some  hot  fuming  nitric  acid  in  a  test  tube. 

3.  The  preparation  of  NO  by  the  reduction  of  dilute  HN03 
with  copper.    To  be  performed  as  usual.    Show  that  NO 
combines  with  oxygen  to  form  N02  and  that  this  dis- 
solves in  cold  water  forming  HN03+HN02. 

4.  The  extreme  reduction  of  the  nitrogen  in  the  nitrate  ion 
by  means  of  a  metal  very  high  in  the  electromotive  force 
table    (see   page   110), — e.   g.   zinc   or  aluminium:   take 
concentrated  sodium  hydroxide  solution,  add  a  little  of 
a  nitrate,  then  add  either  one  of  these  metals  in  the  form 
of    shavings    or    powder.     Warm    the     mixture.     After 
violent  reaction  has  set  in,  the  odor  of  ammonia  can  be 
easily  noticed. 

5.  Treat  some  cold,  freshly  prepared,  ferrous  sulphate  solu- 

tion with  dilute  HN03.  A  black  compound  (of  FeS04, 
NO)  will  be  formed.  Heat  the  mixture  to  boiling.  The 
NO  escapes,  and  the  reddish  brown  color  of  the  solution 
shows  the  presence  of  ferric  iron. 

6.  Pass  H2S  through  warm  dilute  HN03.     Sulphur  and  NO 

will  appear. 

In  order  to  consider  properly  the  oxidizing  actions  of  HN03 
the  following  facts  must  be  noted:— 

The  nitrogen  in  nitric  acid  and  in  nitrates  is  in  the  highest 
state  of  oxidation  in  which  it  ever  occurs;  and  the  nitrogen  in 
ammonia  or  ammonium  compounds  is  in  the  lowest  state  of 
oxidation, — it  cannot  be  reduced  further.  Between  these  two 
limits  there  are  a  number  of  oxidation  stages,  the  order  and  re- 
lation of  which  is  shown  in  the  following  table.  Note  that  the 
free  element  occupies  an  intermediate  position. 


106  University  of  Texas  Bulletin 

Nitrogen 
Name.  Ion. 

Nitric  acid,  HN03  and  nitrates N5* 

Nitric  peroxide  or  nitrogen  textroxide,  N02  or  N204 ....  N4* 

Nitrous  acid,  HN02  and  nitrites N3* 

Nitric  acid  or  nitrogen  dioxide,  NO N2* 

Hyponitrous  acid,  NHO,  and  nitrous  oxide  N20 N* 

Nitrogen,  N2 N° 

Ammonia,  and  its  salts,    (NHJ  * N3 ' 

The  equations  for  the  experiments  above  may  now  be  de- 
rived. 

Experiment  (3).  When  completely  ionized,  HN03  is 
H*,  N5*,  30")-  Since  the  nitrogen  finally  appears  as  NO,— i.  e. 
(N2*,  O") — it  has  received  3( — ),  three  electrons.  Since  these 
electrons  are  obtained  from  Cu°  becoming  Cu2*,  it  follows  that 
these  two  substances  must  change  in  the  ratio  3Cu  to  2HN03 
in  order  that  the  number  of  electrons  given  up  by  the  Cu  shall 
be  completely  taken  up  by  the  changing  HN03.  But  when 
2HN03  change  (to  2NO),  then  2H*  and  40"  will  become  free 
ions,  and  since  0"  ions  cannot  remain  free  in  the  presence  of 
H*  ions,  they  will  form  4H20.  This  requires  8H*,  for  which 
the  2HN03  just  considered  supply  only  2H*,  and  6  extra  HN03 
must  give  up  their  H*  ions.  The  6NO3'  from  these  6HN03 
balance  up  with  the  3Cu**  formed  in  this  action.  Considering 
all  this  we  write — 
3Cu°  +2HN5*03+6HNO3=3Cu(NO3)2+2NO+4H2O 

to  2*  to  2* 

Which  substance  is  oxidized?  which  reduced?  Is  the  amount 
of  oxidation  equal  to  the  amount  of  reduction? 

Experiment  (4).  In  the  change  from  nitrate  ion  to  ammonia, 
each  "N"  receives  8  electrons,  while  each  "Al"  gives  up  3  elec- 
trons ;  hence  the  ratio  between  the  number  of  Al  and  the  number 
of  N03'  which  change  simultaneously  is 

8A1:3NO8' 

In  the  presence  of  sodium  hydroxide,  the  Al***  ion  combines 
with  INa*  and  20"  to  form  NaA102.    The  N3'  ion  forms  NH3, 


Note. — All  aqueous  solutions  contain  H*  and  O"  ions,  and  when  these 
free  ions  are  used  up  more  will  be  formed  by  further  ionisation. 


Chemistry  in  High  Schools  107 

hence  it  combines  with  3H*.     Considering  all  this,  we  arrive  at 
the  following  equation:— 

8A1°  -f  3NaN5*O3+5NaOH+2H2O==8NaAlO2+  3NH3. 

to  3»  to  3' 

Which  element  or  substance  is  oxidized?  which  reduced?  Is 
the  amount  of  oxidation  equal  to  the  amount  of  reduction? 
These  questions  should  be  asked  in  connection  with  all  equa- 
tions of  oxidation  and  reduction. 

Exp.  (5).  One  Fe**  gives  up  one  electron  to  become  Fe***, 
and  since  the  nitrogen  is  reduced  from  HN03  to  NO  (i.  e.,  3  elec- 
trons are  taken  up  by  1  N),  then  the  ratio  between  the  valence- 
changing  substances  is  3  FeS04  :HN03.  The  other  considerations 
are  the  same  as  in  (3)  above.  The  equation  arrived  at  is:— 
3Fe**S04+HN5*03+3HN03= 

to  3»  to  2* 

Fe2  (SOJ  3+Fe  (N08)  8+NO+2H20. 

Exp.  (6).  S"  ions  change  to  S°.  Since  NO  is  formed  from 
NO3',  the  ratio  between  the  valence-changing  substances  is 

3H2S  :2HNO3. 
Hence  the  equation  is: — 

3H2S2'  +2HN5*03==2NO+3S-f4H2O. 

to  0  to  2* 

One  more  equation  should  be  added  here:  the  reaction  of 
''aqua  regia. "  Considering  that  NO  is  the  reduction  product 
and  free  chlorine  is  the  oxidation  product,  the  ratio  between  the 
valence  changing  substances  must  be 

3HC1:1HN08 
and  the  equation  is 

3HC1  '-fHN5*03=2H20+3Cl+NO. 

to  0          to  2* 

The  foregoing  arithmetic  considerations  are  second  in  impor- 
tance to  the  real  chemical  knowledge  to  be  gained  from  the  ex- 
•periments  above.  The  latter  consists  of  knowing  what  particular 
products  of  oxidation  or  reduction  are  obtained  under  particular 
circumstances.  This  must  be  remembered.  The  "chemical"  as- 
pect of  the  experiments  with  nitric  acid  involves  the  following 
general  facts  (see  also  the  Table  of  Electromotive  Forces  of 
Battery  Poles)  :— 

The  extent  of  reduction  of  nitrogen  in  compounds  depends 


108  University  of  Texas  Bulletin 

upon  the  strength  of  the  reducing  agent  and  upon  the  dilu- 
tion of  the  nitrogen  compound.  For  example,  with  dilute  nitric 
acid,  copper  produces  NO,  while  zinc  produces  nitrogen.  Again, 
with  concentrated  nitric  acid,  copper  produces  N02;  and  with 
very  dilute  nitric  acid,  zinc  reduces  the  nitrogen  from  nitric  acid 
to  ammonia. 

These  general  relations  should  be  impressed  by  drill  with  spe- 
cial examples  as  illustrated  in  the  following  exercise. 

Exercise. 

1.  Figure  out  the  equation  of  the  reaction  that  takes  place 
when  copper  sulphide  is  dissolved  in  dilute  nitric  acid  if  at  the 
end  the  sulphur  is  present  as  free  sulphur  and  the  nitrogen  as 
nitric  oxide. 

2.  Do  the  same  with  bismuth  sulphide,  and  again  with  silver 
sulphide. 

3.  If  aqua  regia,  after  its  preparation  by  mixing  the  acids,  is 
essentially  a  solution  of  chlorine  (see  equation  above),  what  will 
be  the  equation  for  its  action  upon  mercuric  sulphide  which  re- 
sults in  a  solution  of  mercuric  chloride? 

4.  Note  the  position  of  silver,  relative  to  copper,  in  the  Elec- 
tromotive Force  Table,  page  110,  and  hence  infer  what  will  be 
the  probable  reduction  product  of  nitric  acid  if  the  concentrated 
acid  reacts  with  silver.    Write  the  equation  for  this  action. 

5.  Do  the  same  for  lead  and  dilute  nitric  acid ;  and  again  for 
cadmium  and  very  dilute  nitric  acid. 

Note  on  the  Oxidizing  Action  of  Sulphuric  Acid.  Sulphuric 
acid  is  occasionally  used  as  an  oxidizing  agent.  The  student 
may  have  occasion  to  meet  it  in  connection  with  the  dissolution 
of  metals  in  it,  or  in  its  action  upon  potassium  bromide  and  potas- 
sium iodide.  Since  the  reduction  products  of  sulphuric  acid  are 
all  known  to  the  student,  it  is  advisable  to  add  here  the  few  re- 
marks necessary  to  inform  him  fully  concerning  these  particular 
reactions. 

The  order  of  the  reduction  products  of  sulphuric  acid  and  of 
their  ions  is  as  follows: 


Chemistry  in  High  Schools  109 

Order  Substance  Ion. 

1  Highest  state  of  oxidation        H2S04  S€* 

2.  Next  lower  H2S03  or  S02  S4» 

3.  Next  lower  S  S° 

4.  Lowest  H2S  S" 
With  weak  reducing  agents  such  as  metallic  silver  and  metallic 

copper  concentrated  sulphuric  acid  will  be  reduced  to  S02  only. 
Of  course  the  sulphate  of  the  metal  is  produced  in  the  reaction. 

With  the  strong  reducing  agents  such  as  zinc,  the  reduction 
product  is  H2S. 

Concentrated  sulphuric  acid  does  not  oxidize  chlorine  from 
HC1;  but  it  oxidizes  bromine  from  bromides  forming  free  bro- 
mine, and  the  sulphuric  acid  itself  is  reduced  the  least  amount 
only,  namely  to  S02.  Iodine  from  iodides  is  so  easily  oxidized 
that  the  sulphuric  acid  is  reduced  to  H2S  even. 

For  a  numerical  exercise,  the  first  five  equations  for  the  five 
reactions  just  mentioned  may  be  figured  out. 

Table  of  Electromotive  Forces  of  Battery  Poles. 

In  the  table  below,  of  electromotive  forces  of  some  battery 
poles,  the  voltages  given  are  those  of  the  cells  formed  by  combin- 
ing each  of  these  poles  with  a  hydrogen  pole,  which  latter  serves 
as  a  zero  or  reference  pole. 

The  prefixed  algebric  signs  indicate  the  polarity  of  the  "  meas- 
ured" pole  in  this  combination. 

The  accompanying  scale  of  these  forces  shows  their  mutual 
relation. 

When  a  pole-component  changes  so  as  to  be  deprived  of  or 
give  up  electrons,  then  it  is  oxidized,  or  acts  as  the  negative  pole 
of  a  battery  cell. 

Any  pole  in  the  table  combined  with  any  other  pole  will  form 
a  battery  cell  the  force  of  which  is  shown  in  the  ' '  Scale  showing 
the  relation  of  EMF's":  it  is  represented  by  the  distance  be- 
tween the  poles.  The  pole  uppermost  in  the  table  acts  as  the 
negative  pole  in  this  combination, — here  oxidation  takes  place. 

When  the  substance  that  would  be  used  up  at  one  pole  during 
the  action  of  a  cell  is  mixed  or  placed  in  direct  contact  with  the 
substance  that  would  be  used  up  at  the  other  pole,  then 


110 


University  of  Texas  Bulletin 


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Scale  showlnr  relation 
of  EMFs. 

-K 
—3.0- 


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— Oa 

—2.0— 

-JAf 

— Al 

-1.0- 


—  Zn 

—  S 


—  Cd 

—  PblO 
-Ni 

—  Pbl8.  8n 
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-Aa.  Sb.  Bl 

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—I 

—  Fel8 


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—  Ol 


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— F 
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Chemistry  in  High  Schools  111 

these  two  substances  react  in  the  same  way  as  in  the  battery 
cell.  Direct  contact  makes  the  connecting  wires,  etc.,  for  the 
transfer  of  the  electrons  unnecessary.  All  mixtures  undergoing 
oxidation  and  reduction  reactions  may  be  considered  to  be  made 
up  in  this  way. 

The  substances  in  the  higher  states  of  oxidation  (in  the  wide 
column  on  the  left)  are  all  oxidizing  agents :  they  appear  in  the 
ascending  order  of  strength  as  oxidizers. 

The  reducing  agents  are  in  the  column  on  the  right:  they  ap- 
pear in  the  descending  order  of  strength  as  reducers. 

Any  reducing  agent  in  the  table  will  react  with  any  oxidizer 
below  it  in  the  table.  The  following  two  common  examples  of 
this  fact  should  be  noticed : 

(a)  Any  metal  in  the  table  will  displace   (reduce)  any  metal 
below  it  from  a  solution  of  its  simple  salts.     Thus,  zinc  or  iron 
will  displace  copper  from  copper  sulphate,  silver  from  silver 
nitrate,'  or  hydrogen  from  hydrochloric  acid. 

(b)  Anyone  of  the  non-metals  (Cl,  Br,  I,  S),  will  be  displaced 
(oxidized)  from  its  simple-ion  compounds  (chlorides,  bromides, 
iodides,  sulphides),  by  any  one  of  the  non-metals  below  it  in  the 
table.     Thus,  chlorine  liberates  bromine  from  bromides,  sulphur 
from  sulphides,  etc. 

The  metals  above  zinc  in-  the  table  below,  and  fluorine,  cannot 
be  used  as  poles  for  practical  batteries,  or  as  reducing  (respect- 
ively, oxidizing)  agents  in  ordinary  chemical  (aqueous)  mix- 
tures because  these  elements  react  with  water. 

Note  on  the  potential  of  chlorine:  its  potential  is  less  noble 
("noble"  means  the  direction  in  the  table  from  hydrogen  to- 
wards gold)  if  the  concentration  of  the  free  chlorine  is  less  or  if 
the  concentration  of  the  chloride  compound  is  greater  than  as 
given  in  the  table.  Hence  the  formation  of  the  first  portions  of 
free  chlodine  in  a  concentrated  solution  of  hydrochloric  acid 
will  take  place  with  a  potential  between  +1.35  and  +1.0  volts. 
This  explains  why  nitric  acid  oxidizes  hydrochloric  acid. 

Note  on  the  "Back"  Electromotive  Force  of  the  Poles  During 
Electrolysis. 

The  products  formed  at  the  poles  during  electrolysis  exert 
an  "opposing"  electromotive  force,  i.  e.  "opposed"  to  the  ap- 


112  University  of  Texas  Bulletin 

plied  force.  They  exert  about  the  same  force  as  the  battery 
poles  composed  of  the  same  materials. 

Of  different  chemical  changes  possible  at  the  cathode  of  any 
particular  cell  that  one  will  take  place  which  will  exert  the  least 
"zincic"  potential  (zincic  means  the  direction  in  the  table  from 
hydrogen  toward  zinc). 

At  the  anode  that  particular  change  will  take  place  which  re- 
quires the  least  "  noble  "  potential. 

For  the  liberation  of  hydrogen  on  metals  other  than  platinum, 
a  more  zinzic  voltage  is  required  than  for  platinum.  This  addi- 
tional voltage  amounts  to  as  much  as  0.5 — 0.7  volts  for  the  metals 
lead,  zinc,  and  mercury. 


Chemistry  in  High  Schools  113 


APPENDIX. 

The  Details  of  Construction,  Action  and  Operation  of  Alter- 
nating Current  Rectifyers. 

The  Action  of  the  Electrolytic  Cell. 

The  electrolytic  cell  used  to  "rectify"  the  alternating  cur- 
rent, as  ordinarily  constructed,  has  one  pole  of  aluminium,  the 
other  of  lead,  and  between  them  a  solution  of  sodium  phos- 
phate. When  prepared  for  operation,  the  cell  allows  only  that 
alternation  of  the  current  to  pass  which  makes  the  aluminium 
pole  the  cathode,  or  negative  pole,  and  it  prevents  the  passage 
of  the  reverse  alternation,  which  would  make  the  aluminium 
the  anode  or  positive  pole.  This  property  of  the  cell  is  due 
to  the  fact  that  the  aluminium  is  covered  with  a  non-conduct- 
ing film  of  aluminium  hydroxide  or  basic  salt  with  a  gas 
(oxygen)  held  in  its  "meshes"  or  pores.  Such  a  film  over  a 
metal  does  not  prevent  the  passage  of  the  current  when  this 
metal  serves  as  the  cathode;  but  it  hinders  the  passage  of  the 
current  when  this  metal  serves  as  an  anode.  It  is  as  though 
the  cations  need  not  actually  touch  the  metal  of  the  pole  in 
order  to  be  discharged,  while  the  anions  cannot  be  discharged 
unless  they  come  in  direct  contact  with  the  metal  surface. 
Hence  a  cell  in  which  one  pole  is  covered  with  such  an 
insulating  film  and  the  other  not  covered,  or  with  a  "conduct- 
ing" surface,  is  "  uni-directional "  in  its  action. 

The  materials  used  for  this  purpose,  aluminium  and  lead,  are 
particularly  well  suited  for  this  purpose  on  account  of  the  fol- 
lowing advantageous  properties  possessed  by  them : 

(a)  when  a  bare  surface  of  aluminium  is  exposed  to  anodic 
discharge  (in  solutions  of  phosphates,  sulphates,  borates,  etc.) 
a  film  (of  aluminium  hydroxide)  is  almost  immediately 
formed;  and  this  film  is  not  disturbed  by  any  cathodic  dis- 
charge such  as  takes  place  in  sodium  salt  solutions.  Hence 
when  a  bare  aluminium  pole  is  connected  with  an  alternating 
current,  that  alternation  which  makes  it  the  anode  will  quickly 
cover  it  with  such  an  insulating  film,  and  the  formation  of  this 


114  University  of  Texas  Bulletin 

film  will  not  be  hindered  by  the  reverse  alternation  of  the  cur- 
rent. 

(b)  a  lead  pole,  which  in  the  rectifier  acts  mostly  as  the 
anode,  has  its  surface  converted  to  lead  peroxide  by  the  anodic 
discharge,  and  this  material,  in  contradistinction  to  the  alumin- 
ium film  is  a  good  conductor.  If  the  lead  acts  as  a  cathode, 
this ,  peroxide  is  reduced  to  metallic  lead.  Thus  neither  anodic 
nor  cathodic  action  covers  the  lead  with  an  insulating  layer. 

With  high  voltages,  or  hot  solutions,  the  aluminium  film 
breaks  down  frequently  in  its  weaker  spots,  and  considerable 
leakage  of  current  occurs.  Free  acid  in  the  electrolyte  also 
increases  the  leakage  current.  But  with  cold,  neutral  solutions 
and  a  voltage  below  70  volts,  the  leakage  current  is  not  exces- 
sive. 

Construction  of  Large  Electrolytic  Jars  for  Rectifier  Set  No.  1. 

Secure  2  jars  of  2  to  4  quarts  capacity,  with  a  depth  of  from 
7  to  11  inches.  Have  a  carpenter  cut  4  discs  of  one-inch  pine 
lumber,  two  discs  of  a  size  to  fit  inside  of  the  upper  edge  of 
the  jar,  and  the  other  two  to  fit  over  the  top  of  the  jar.  By 
means  of  screws  fasten  one  of  the  smaller  and  one  of  the  larger 
discs  together  with  the  grains  of  the  two  pieces  at  right  angles 
to  each  other;  cut  a  rectangular  hole  through  the  center  of 
these  discs  of  such  a  size  that  the  aluminium  plate  which  is  to 
be  used  will  just  pass  through  this  hole.  One  side  of  the  hole 
should  be  cut  practically  vertical,  the  other  should  be  cut 
slantingly  so  that  a  suitable  thin  wedge  inserted  on  the  slant- 
ing side  of  the  hole  may  serve  to  hold  the  aluminium  plate 
rigidly  in  a  vertical  position  when  this  wooden  cover  is  placed 
on  top  of  the  jar.  Secure,  by  mail,  from  the  U.  S.  Aluminium 
Co.  (Pittsburgh,  Pa,  or  Old  Colony  Bldg.,  Chicago,  111.),  speci- 
fying the  softest  grade  for  which  their  stock  number  is  2SO, 
four  aluminium'  plates  3  inches  wide,  12  inches  long,  1-8  inch 
thick,  13-5  lbs.,- which  will  cost  80  cents.  Drill  a  hole  near  one 
end  of  each  of  two  plates  to  screw  on  a  binding  post.  (It  is 
almost  impossible  to  fasten  the  connecting  wires  on  the  alu- 
minium by  soldering.)  Another  way  to  fasten  the  connecting 
wire  is  to  drill  a  hole  about  the  size  of  the  wire  through  the 


Chemistry  in  High  Schools  115 

upper  edge  of  the  plate,  put  in  the  end  of  the  wire,  and  clamp 
it  by  hammering  the  plate  together  at  that  point.  Secure  from 
a  plumber  four  strips  of  sheet  lead  about  3  to  4  inches  wide,, 
6  to  7  inches  long  and  thick  enough  to  be  stiff.  Flatten  each 
out  thoroughly,  and  at  one  end  bend  a  strip  %  inch  wide, 
sharply  at  right  angles  to  the  rest  of  the  plate;  on  this  strip 
solder  the  end  of  a  6  to  10  inch  piece  of  copper  wire  (No.  14). 
By  means  of  brass  screws  driven  through  this  strip  into  the 
wooden  cover,  fasten  two  lead  plates  to  the  under  side  of  each 
cover,  so  that  they  will  be  parallel  to  the  aluminium  plate  at  a 
distance  of  %  to  %  inch,  one  on  each  side.  Then  dip  the 
wooden  cover  into  hot  paraffin,  so  that  all  the  wood  and  the 
lead  plate  fastenings  will  be  covered  with  it.  Insert  the  alu- 
minium plates,  fill  the  jars  three-fourths  full  with  the  phos- 
phate solution  (prepared  as  directed  below),  and  make  the  con- 
nections shown  in  Fig.  6. 

The  two  jars  may  be  reduced  to  one  by  placing  both  alumin- 
ium poles  in  the  same  jar  with  one  lead  plate  between  them 
and  one  on  the  outside  of  each  aluminium  plate.  Thus  three 
lead  plates  are  used,  which  are  all  connected  to  the  same  ter- 
minal. The  connections  are  the  same  as  with  two  jars.  , 

i 
,--...} 

Design  and  Action  of  Special  Transformer. 

The  transformer  to  be  used  in  this-  connection  is  made  of  only 
one  coil.  One  connection  for  the  current  to  be  drawn  from  it 
is  at  the  center  of  the  coil  (see  Figure  6).  The  " positive" 
direct  current  flows  outward  from  this,  or  in  other  words,  this 
is  the  direct  current  +  pole  connection.  In  addition  there  are 
other  pairs  of  connections  to  the  coil,  the  two  connections  of 
each  pair  being  " balanced"  with  reference  to  the  center,  i.  e., 
between  the  center  and  one  connection  there  are  as  many  ' '  turns 
of  wire"  as  between  the  center  and  other  connection  of  a  pair. 
One  connection  of  each  pair  may  be  connected  with  the  alumin- 
ium pole  of  one  cell,  and  the  other  to  the  aluminium  pole 
of  the  other  cell.  The  lead  poles  of  the  two  cells  are  connected 
to  a  common  wire  from  which  the  negative  direct  current  flows, 
in  other  words,  it  is  the  direct  current — pole  connection. 


116  University  of  Texas  Bulletin 

The  voltage  between  any  two  points  of  the  primary  coil  of  a 
transformer  is  practically  such  a  fraction  of  the  voltage  of  the 
primary  circuit  as  the  ratio  that  the  number  of  "turns  of 
wire"  intercepted  on  the  coil  by  the  two  points  bears  to  the 
number  of  turns  in  the  whole  coil.  Hence  between  the  center 
and  either  extremity  one-half  of  the  primary  voltage  is  ob- 
tained, and  between  the  center  and  any  other  points,  lesser  volt- 
ages proportionate  to  the  number  of  turns  between  it  and  the 
center  are  obtained. 

The  direction  of  the  electric  pressure  (or  sign  of  the  voltage) 
on  one  side  of  the  centre  is  the  opposite  of  that  exerted  simul- 
taneously at  the  other  side.  If  at  any  particular  moment  the 
voltage  on  the  left  of  the  centre  is  such  as  to  make  the  left  con- 
nection negative,  then  this  would  tend  to  send  a  current  into 
the  (left)  cell  with  which  it  is  connected,  thus  making  the 
aluminium  pole  of  this  cell  the  cathode,  and  the  lead  pole  the 
anode.  Under  these  conditions  the  aluminium  pole  opposes  no 
hindrance  to  the  passage  of  the  current.  However,  exactly  the 
reverse  condition  exists  simultaneously  at  the  connection  to  the 
right  of  the  center  of  the  coil  and  the  aluminium  pole  in  this 
second  cell  opposes  (practically  prevents)  the  passage  of  the 
current  from  this  side.  With  the  next  alternation  of  the  cur- 
rent all  the  conditions  are  reversed.  This  time  the  current  is 
free  to  flow  through  the  cell  on  the  right,  but  it  cannot  flow 
through  the  cell  on  the  left.  Thus  the  current  which  flows  out 
of  the  coil  at  the  centre  is  always  positive,  but  it  comes  from  the 
right  side  of  the  coil  at  one  moment,  and  from  the  left  side  at 
the  next  moment. 

In  ordering  such  a  coil  suitable  for  "Rectifying  Sets  No.  1" 
above,  the  following  should  be  specified: — the  transformer  is 
to  be  of  the  single  coil  or  "auto"  type,  and  is  to  be  designed 
for  a  "110  volts,  60  cycle"  circuit;  capacity,  5  amperes  at  110 
volts.  It  is  to  be  without  case,  but  equipped  with  frame  cast- 
ings in  order  that  it  may  be  fastened  to  the  table  or  wall.  The 
following  connections  are  to  be  made — nine  leads  to  be  con- 
nected as  follows: 

Two,  at  the  ends  of  the  coil — for  the  main  line. 

One,  at  the  centre. 


Chemistry  in  High  Schools  117 

Three  pairs  for  connections  to  be  " balanced"  with  reference 
to  the  central  tap  and  connected  to  the  coil  so  as  to  secure  the 
following  voltages  (approximately)  : 

13%  volts  between  the  center  and  either  one  of  the  first  pair. 

27%  volts  between  the  center  and  either  one  of  the  second 
pair. 

41*4  volts  between  the  center  and  either  one  of  the  third  pair. 

In  other  words,  the  transformer  is  designed  for  eight  circuits  of 
13%  volts  each. 

The  Moloney  Electric  Co.  of  St.  Louis,  Mo.,  will  furnish  such 
a  transformer  for  $13.00  or  slightly  less,  the  general  appearance 
of  which  is  shown  on  page  43  of  their  catalogue. 

Preparation  of  Solution  for  Electrolytic  Jars. 

For  each  quart  of  solution  use  one-half  pound  of  sodium  phos- 
phate crystals,  and  add  phosphoric  acid  in  small  portions  until 
the  mixture  does  not  turn  litmus  paper  a  deep  Hue,  but  a  lighter 
shade — not  pink,  however. 

Operation  of  the  Rectifier  Set  No.  1. 

When  the  current  is  to  be  turned  on  for  the  first  time  after  the 
rectifier  has  been  assembled  (or  for  the  first  time  after  a  long 
period  of  rest)  the  lowest  alternating  current  voltage  should  be 
connected  to  the  electrolytic  cells,  and  this  should  remain  con- 
nected at  least  several  minutes  before  any  higher  voltage  may  be 
connected.  After  that  no  further  precaution  need  be  taken.  In 
the  absence  of  an  insulating  layer  over  the  surface  of  the  alumin- 
ium the  current  will  pass  direct  through  both  cells,  but  the 
liquid  resistance  of  the  cells  will  be  large  enough  to  prevent  this 
current  from  being  excessively  large  if  the  voltage  is  small.  This 
current  in  passing  forms  the  films  over  the  surface  of  the  alu- 
minium plates. 

During  action  aluminium  phosphate  is  slowly  formed  and 
appears  as  a  white  flocculent  sediment.  Thus  the  aluminium 
pole  and  the  phosphate  ion  (the  P04  radical)  are  used  up  very 
slowly.  Hydrogen  also  is  discharged  at  the  cathode.  To  re- 


118  University  of  Texas  Bulletin 

place  this  loss,  small  amounts  of  phosphoric  acid  must  be  added 
to  the  solution  from  time  to  time,  with  the  aid  of  litmus  as  in 
preparing  the  solution.  Naturally,  any  water  lost  by  evapora- 
tion must  be  replaced.  Under  these  conditions  the  cells  will 
operate  practically  indefinitely. 

Depending  upon  the  rate  at  which  the  current  is  drawn, 
the  voltage  of  the  direct  current  obtained  will  be  from  10  to  25 
volts  less  than  the  alternating  current  voltage  applied  to  the 
electrolytic  jars. 

When  a  current  greater  than  5  amperes  is  drawn  continuously 
for  more  than  an  hour,  the  liquid  in  the  electrolytic  jars  is 
heated  so  rapidly  that  it  may  finally  become  too  hot  for  safe  or 
economical  operation.  Hence  when  large  currents  are  needed 
for  longer  periods  of  time,  the  electrolytic  jars  must  be  cooled 
in  some  way.  This  can  be  done  by  replacing  the  glass  jars  by 
heavy  tin  or  sheet  iron  cans  of  the  same  size  (which  can  be 
made  by  any  tinner),  and  placing  these  electrolytic  vessels  in 
a  large  vessel  filled  with  cold  water.  In  extreme  cases,  ice  water 
may  be  used. 

A  Small  Cheap  Rectifier. 

Secure  a  1  quart  fruit- jar  or  a  similar  vessel.  Secure  a. 
strip  of  sheet  lead  about  3  inches  wide  and  10  to  12  inches  long. 
Hang  this  lengthwise  into  the  jar,  along  the  wall,  and  clamp  it 
in  position  by  bending  the  upper  end  over  the  rim,  and  solder 
a  connecting  wire  to  this.  Fasten  a  wooden  cover  (6x6  inches) 
on  the  top  of  the  jar  by  means  of  pieces  of  wood  nailed  as 
cleats  to  the  under  side  of  the  cover.  Secure  by  mail,  from  the 
U.  S.  Aluminium  Co.  (Pittsburgh,  Pa.,  or  Old  Colony  Bldg., 
Chicago)  rods  of  aluminium  %  to  %  inches  in  diameter,  and 
10  to  12  inches  long.  Specify  the  softest  grade  (Cat.  No. 
280).  Four  rods  V2xl2  inches,  will  cost  50  cents. 

To  fasten  a  copper  connecting  wire  to  the  aluminium  rods, 
drill,  near  one  end  of  each,  a  hole  large  enough  to  admit  the 
wire.  When  making  connection  insert  the  wire  and  clamp  it 
by  a  few  blows  of  a  hammer  on  the  side  of  the  rod.  Near  the 
center  of  the  cover,  bore  one  (or  two)  holes  of  the  exact  size 
of  the  aluminium  rods,  so  that  the  rods  extending 


Chemistry  in  High  Schools 


119 


through  these  holes  will  be  held  in  vertical  position.  Con- 
nect this  cell  in  series  with  either  a  lamp-bank  or  a  suit- 
able rheostat.  The  lamp-bank  should  have  8  to  12  incan- 
descent lights  of  32  candle-power,  all  connected  in  parallel. 
In  place  of  this  lamp-bank  it  will  be  more  convenient  to  use  a 
11  theatre  dimmer"  for  12  lights  (Ward-Leonard  Electric  Co., 
BronxviUe,  N.  Y.  (Cat.  No.  SD  16),  price  about  $2.50).  After 
filling  the  jar  with  sodium  phosphate  solution,  the  rectifier  is 
ready  for  use  and  can  be  used  without  any  particular  precau- 
tions. 

How  to  Rectify  Both  Alternations  Without  a  Transformer. 

Without  the  aid  of  the  special  transformer,  the  only  way  to 
rectify  both  alterations  is  to  use  four  simple  cells  and  connect 
them  as  shown  in  Fig.  7.  It  is  absolutely  necessary  to  insert  a 
large  resistance  in  the  alternating  current  circuit  until  the  sur- 
faces of  the  aluminium  plates  are  formed.  For  this  purpose 
cells  of  the  size  first  described  above  require  two  32  c.  p.  lamps. 
As  the  surface  "forms"  the  lamps  become  dim.  Then  the  lamps 
may  be  taken  out  of  the  circuit  because  the  film  is  able  to  stand 
110  volts.  A  single-pole,  double-throw  switch  is  usually  used 
to  facilitate  this  change.  The  direct  current  obtained  from  this 
rectifier  will  have  a  voltage  of  80  to  95  volts.  If,  as  is  usually 
the  case  in  laboratories,  the  current  is  to  be  used  at  a  low  volt- 
age, a  lamp-bank  or  some  "high  resistance"  rheostat  must  be 
inserted  in  the  circuit,  either  in  the  alternating  or  in  the  direct 
current  side. 

This  form  of  rectifier,  together  with  its  necessary  accessories, 
costs  fully  as  much  as  the  first  rectifier  described,  and  is  less 
convenient  and  less  suitable. 


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filvm  (QJ 


A  Four- jar   Rectifier  (without  transformer) 


14  DAY  USE 

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